The Thirteenth International
The Thirteenth International
The Thirteenth International
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<strong>The</strong> <strong>Thirteenth</strong><br />
<strong>International</strong><br />
Technical<br />
Conference on<br />
Experimental<br />
Safety Vehicles<br />
Sponsored by:<br />
U.S. Department of<br />
Transportation<br />
National Highway Traffic<br />
Safety Administration<br />
Hosted by:<br />
French Government<br />
Held at:<br />
Paris, France<br />
November 4-7, 1991
Introduction<br />
<strong>The</strong> Intcrnarional Experimcntal Safety Vehicles (ESV)<br />
Program originated under NATO's committee on the Challcnges<br />
of Modern Socicty (CCMS) and was implemcntcd<br />
through bilateral agrecments between the United Statcs<br />
Governmcnt and thc governmcnts of France, the Fedcral<br />
Republic of Germany, Italy, rhc United Kingdom, Japan,<br />
and Swedcn. <strong>The</strong> participlrting nations agrecd to develop<br />
experimental safety vehicles to advancc the state"o[-the-art<br />
in safety engineering and to meet pcriodically to cxchange<br />
technical inforrnation on their progress.<br />
To ditte, twelvc international conferences have been hcld.<br />
each hosted by one of the ptrticipating Governlnents. <strong>The</strong>se<br />
conferences havc drawn participants from government, lhe<br />
worldwide automotive industry, and the motor vehicle safcty<br />
research communily. <strong>International</strong> cooperatior) in motor<br />
vehicle safety research conlinues at the highest level. As<br />
work on experimentrl safety vchicles was completed, the<br />
research program expanded to covcr the entire rangc of<br />
motor vehiclc safety. Thc ESV Conferences now servc ils<br />
the international forum through which progress in motor<br />
vehiclc safety technology is reportcd.<br />
<strong>The</strong> procecdings of each Conlerence have been putrlished<br />
by the United States Covernment and distribured worldwide.<br />
<strong>The</strong>se reports, which detail the safcty research efforts<br />
underway worldwide, have bccn recognizcd as the definitive<br />
work on motor vehicle safcty resea-rch. We are sure<br />
that this outstanding example of internalional cooperation<br />
seeking reductions in motor vehiclc dcaths and injurics will<br />
continue its past succcss.<br />
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Attendees<br />
AUSTRALIA<br />
Brian Fildes<br />
Monash University<br />
Accident Rescarch Centrc<br />
Michacl Griffiths<br />
Roads & Traffic Authority<br />
Peter Makeham<br />
Dept. of Transport<br />
Jack Mcl,ean<br />
Univcrsity of Adclaide<br />
BELGIUM<br />
Tadaomi Akiba<br />
Nissan European Tech. Center<br />
Kazuhito Asakawa<br />
I.A.S.l.C.<br />
Kazuhiko Hayashi<br />
Toyota Motor Europe<br />
Yoshihiro Heishi<br />
Nissan Europcan Tech, Center<br />
Herbert Hennsler<br />
c.E.E.<br />
Susumu Ino<br />
Daihatsu Motor Co., Ltd.<br />
Henk Mannekcns<br />
Nissan European Tech. Center<br />
Masami Misaki<br />
Nissan European Tech, Center<br />
Hideo Obara<br />
Nissan European Tech. Center<br />
Keiichi Okabayshi<br />
Toyota Motor Europe<br />
Ushio Ueno<br />
Toyota Motor Europe<br />
Yves Van der Straaten<br />
Ceneral Motors Europe<br />
Hans Van Driessche<br />
Honda Motor Europe<br />
Daniel Verdiani<br />
Commission of European<br />
Communities<br />
Udo Westfal<br />
ACEA<br />
BULGARIA<br />
Krouin Valkov<br />
Ministry of Transport<br />
CANADA<br />
Duncan McPherson<br />
University of British Colombia<br />
James Newman<br />
Biokenetics Assoc. Ltd.<br />
Stcphen I{ead<br />
University of Waterloo<br />
Christopher Wilson<br />
Road Safety & Motor Vehicle<br />
Ilegulations<br />
CZECTIOSLOVAKIA<br />
Vojtech Rieger<br />
U.S.M.D.<br />
DENMARK<br />
Per Frederiksen<br />
|ustice Ministry - Road Safety Div.<br />
Ib Rasrnussen<br />
Ministry of Justice,/Road Safety<br />
FRANCE<br />
Alain Achard<br />
Renault<br />
Francois Alonzo<br />
I.N.R.E.T.S.<br />
Yves Aubin<br />
Conrite dcs Const. Franc. d'Auto,<br />
Claude Aubry<br />
Autoliv Klippan<br />
Eugene Auffray<br />
F.F.C.<br />
Daniel Augello<br />
Renault<br />
Jean-Jacques Azuar<br />
Chausson Engineering<br />
Jcan Barge<br />
E.C.I.A.<br />
Marc Behaghel<br />
Comite des Const. Franc. d'Auto,<br />
Agncs Bellini<br />
L.A.B./PSA - Itenault<br />
Farid Bendjallal<br />
L.A.B./PSA - I{r.nault<br />
f. M. Bcrard<br />
D.S.C.R.<br />
Itoger Biard<br />
I.N.R.E.T.S. - L.C.B.<br />
Pierre Bigot<br />
P.S.A. I)eugeot Citroen<br />
Georges Blanc<br />
Autornobile Normalisation Bureau<br />
Charlt's Blanot<br />
Renault - Direction dcs Etudes<br />
Jean Bloch<br />
I.N.R.E.T.S.<br />
Jcan-Claude Bluct<br />
I.N.R.E.T.S.<br />
Felix Bocaly<br />
Peugcot S.A. Research<br />
Marc Bocque<br />
Peugeot S.A.<br />
Sergc Bohers<br />
Peugcot 5.A.<br />
fean Bonnoit<br />
I.N.R.E.T.S. - LBA<br />
Veronique Bordes<br />
I.N.It.E.T.S.<br />
- LBA<br />
Antoine Bossard<br />
Automobilcs Ireugeot<br />
Patrick Botto<br />
RCNAUIT.IITACBA<br />
Laurent Bouchard<br />
I{enault - IRBA<br />
Robert Bouquet<br />
I.N.R.E,T.S. - L.C.B.<br />
Denis Bourcart<br />
Autoliv Klippan<br />
]ean-Luc Brard<br />
Peugcot 5.A. I{esearch<br />
Picrrc Brun<br />
P.S.A.<br />
Fra ncoisc' Brun-Cassan<br />
L.A.B./PSA<br />
- Rcnault<br />
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ISth tnternetlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
Gilles Brutel<br />
Peugeot S.A. Research<br />
Jean-Loup Burgaud<br />
Ecole Centralc de Paris<br />
Marie-Christine Cailleret<br />
Renault - IRACBA<br />
Herve Calmelly<br />
Matra Automobiles<br />
Serge Care-Colin<br />
C.E.T.E. de l'Est<br />
Roland Caroff<br />
Peugeot S.A.<br />
Nelson Casadei<br />
Renault. Research Directorate<br />
Francoise Cassan<br />
Rcnault<br />
Claude Cavellero<br />
I.N.R.E.T.S. - LBA<br />
Dominique Cesari<br />
I.N.R.E.T.S. - L.C.B.<br />
Francois Chamouard<br />
Renault - Biomech./Accident lab<br />
Paul Charlety<br />
Autoliv Klippan<br />
Remi Chavanne<br />
Automobiles Peugeot - Sochaux<br />
Martine Chereau<br />
Peugeot S.A. Research<br />
Claude Chevalier<br />
Fondation M.I.A.F.<br />
Jean Chewier<br />
R.A.T.P.<br />
Jean-Picrre Cheynet<br />
u.T.A.C.<br />
Alain Clerc<br />
Automobiles Peugeot<br />
Pierre Colinot<br />
P.S.A. Dircction des Etudes<br />
Par-rl Philippe Cord<br />
LTVBAG<br />
Franck Dauvilliets<br />
Renault - AARMT<br />
Christophe de Baynast<br />
Peugeot S.A. Research<br />
Pascal Deloof<br />
INRETS - CRESTA<br />
Igor Demay<br />
Automobiles Citroen<br />
Andre Dcperrois<br />
P.S.A.<br />
fean Derampe<br />
Peugeot S.A.<br />
Veronique Desgardins<br />
Automobile Citroen<br />
Iambert Detoux<br />
F.F.C.<br />
lnuis DeVaulx<br />
P.S.A.<br />
Serge Diet<br />
Renault<br />
Georges Dobias<br />
I.N.R.E.T.S.<br />
Claude Dolivet<br />
I.N.I{.E.T.S. - L.C.B.<br />
Marie-France Dondel<br />
Renault - Direction des Etudes<br />
Regis Dornez<br />
Renault<br />
Yves Drouadaine<br />
Framasoft CSI<br />
Tour Fiat<br />
Alain Dubos<br />
Renault<br />
Alain Duchesne<br />
Davey Bickford<br />
B. Durand<br />
D.S.C.R.<br />
Marc Ellenbcrg<br />
C.E.T.E. de l'Est<br />
Philippe Eurin<br />
Ministere, Itechcrche/ Technologie<br />
Denis Even<br />
TELMA<br />
Leonce Evin<br />
Auto Klippan<br />
Jean-Pierre Faidy<br />
P.S.A. DRAS<br />
Cerard Faverjon<br />
L.A.B./Peugeot Renault<br />
Andre Fayon<br />
Renault<br />
Michel Ferlay<br />
I.N.R.E.T.S.<br />
Francis Ferrandez<br />
I.N.R.E.T.5.<br />
Serge Ficheux<br />
U.T.A.C.<br />
Claude Fline<br />
Mi ni stere Recherche,/ Technologie<br />
Helene Fontaine<br />
I.N.R,E.T.S.<br />
Jean-Yves Foret-Bruno<br />
Renault<br />
Arnaud Froumajou<br />
Peugeot S.A. Research<br />
Jean Fmctus<br />
U.T.A.C.<br />
Philippc Gaches<br />
Pcugcot S.A. Research<br />
Cilles Garret<br />
Autoliv Klippan<br />
Bernard Cauvin<br />
D.S.C.R.<br />
Louis Germain<br />
Renault Vehicules Industriels<br />
Olivier Gignoux<br />
I{enault<br />
Jean-Claude Goaer<br />
Renault<br />
Camille Gontier<br />
Et:olc Centrale de Paris<br />
Christian Goualou<br />
P.S.A./E,C.P.<br />
Silvie Goujon<br />
Pe'ugeot S.A. Research<br />
Raymond Cuasco<br />
F.I.E.V.<br />
Louis-Rohert Cuy<br />
PYROsPACE<br />
Mouloud Haddak<br />
I.N.R.E.T.S./L.C.B.<br />
Jean Hamon<br />
P.S.A. DRAS<br />
Jean-Marie Heinrich<br />
L.A.B./PSA - Rcnault<br />
Claude Henry<br />
L.A.B./PSA - Renault<br />
Francois Hordonneau<br />
Renault
fean-Francois Huere<br />
Peugeot S.A. Research<br />
Christophe Jacob<br />
Renault - AARMT<br />
facques ]olivet<br />
Autoliv Klippan<br />
Marco Klingler<br />
INRETS _ CRESTA<br />
Serge Koltchakian<br />
Renault - Biomech./Accident I^ab<br />
Michel Kozyreff<br />
Autoliv Klippan<br />
fean facques laine<br />
C.E.T.E., Nord Picardie<br />
Marc laliere<br />
Renault Automobiles Centre<br />
Tcchnique<br />
Patrice larguier<br />
P.S.A. - DRAS<br />
Francois faurent<br />
Pcugeot S.A. Research<br />
Aime Letalve<br />
Rcnault<br />
fean-Yves LeCoz<br />
L.A.B./PSA-Renault<br />
Evelyne l-epoiwe<br />
Renault<br />
Francois Leygue<br />
Ministry of Transport<br />
Richard Loinard<br />
PYROsPACE<br />
Roland Lucquiad<br />
u.T.A.C.<br />
Philippe Mack<br />
Renault<br />
Jean-Paul Magnier<br />
Davey Bickford<br />
Vincent Maillard<br />
E.C.I.A.<br />
Bruno Marguet<br />
GEC ALSTHOM - CIMT<br />
Gerard Martigny<br />
Peugeot S.A. Research<br />
Veronique Martin<br />
Automobiles Citroen<br />
Yves N4artin<br />
Automobiles Citroen<br />
<strong>The</strong>rese Martinet<br />
Peugeot S.A.<br />
Gerard Mauron<br />
Feugeot S.A. I{esearch<br />
Jean-Pierre Medevielle<br />
I.N,I{.E.T.S.<br />
Menard<br />
INNOVATION 128<br />
Serge Morlan<br />
PYR06PACE<br />
Francois Mounier-Poulat<br />
Renault Vchicules Industriels<br />
Richard Najchaus<br />
Renault<br />
Henri Novel<br />
Hulicz France<br />
Sean C/Riordain<br />
I.N.I(.E.T.S. - L.C.B.<br />
laurent Oudcnard<br />
Renault - IRBA<br />
Jean-Frederic OuRers<br />
Automobiles Citroc'n<br />
Jean Pages<br />
F.I.E.V.<br />
Christian Perotto<br />
LIVBAC<br />
Claire Petit<br />
Renault - IRBA<br />
Iohn L. Phelps<br />
o.I.c.A.<br />
Yvette Pincemaille<br />
L.A.B./PSA - Rcnault<br />
Sophie I'lanque<br />
Renault - AARMT<br />
Yves Portier<br />
A.P.S.A.D., Direction Automobile<br />
Daniel Pouget<br />
Renault<br />
Alain Priez<br />
RCNAUIT - IRACBA<br />
Eric Ramaioli<br />
Renault<br />
Michelle Ramet<br />
I.N,R,E,T.S. - L.C.B.<br />
Philippe Ranc<br />
Automobilcs Citroen<br />
Altendees<br />
Raymond Ravenel<br />
Comite de's Const. France D'Auto<br />
Jean-Pascal l{cille<br />
Ilenault. Dircctioh des Etudes<br />
Francois Renaudin<br />
SEI{AM, l;rb. tjc Bicrmccanique<br />
Ioel Rio<br />
Rcrratrlt<br />
Nicholas Rogers<br />
IMMA<br />
Jean-Paul Rouet<br />
SAGEM<br />
Patrice Roulois<br />
He'uliez Automobiles<br />
Nakoto *rkai<br />
NIPTIONDENSO<br />
Rcnc Sallen<br />
Automobiles Citroen<br />
Patrick Siarry<br />
Ecole Centrale dc lraris<br />
Donggang Song<br />
Itenault - II{ACBA<br />
Olivier Soulie<br />
Automobilcs Pcugeot-Sochaux<br />
|ean-Pierre Spagnol<br />
Autoliv Klippan<br />
Georges Stcherbatcheff<br />
Renault<br />
Christian Stcycr<br />
Renault<br />
Xiang-Tong Tao<br />
INRETS LCB<br />
Philippe Tardivon<br />
P.S.A. Dircction des Etudes<br />
Claude Tarriere<br />
Rcnault<br />
Christian <strong>The</strong>venet<br />
C.C,F.A.<br />
Christian Thomas<br />
L.A.B./PSA- Rcnault<br />
Pierre Toursel<br />
Irt-ugtot S.A. Itesearch<br />
Xavier Trosseilk'<br />
Renault<br />
Ierome Uriot<br />
Renault - IRBA<br />
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13th lntemetlonal Tacnnlcal ConferenCe on Experlmental Safety Vehlcles<br />
Harold Vallee<br />
L.A.B./IrSA - Renault<br />
Gilles Vallet<br />
I.N.R.E.T.S.<br />
|acqucs Van Bunderen<br />
Autoliv Klippan<br />
Kyriakos Vavalidis<br />
Autoliv Klippan<br />
Philippe Vcntre<br />
Renault<br />
Michele Vergne<br />
Fondation M.l.A.F.<br />
Roel Vcrhoog<br />
CESA<br />
Iouis-Claude Vrignaud<br />
Siemens Automotive S.A.<br />
Gilbert Walfisch<br />
Renault<br />
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Remy Willingcr<br />
I.N.I{.E.T.S.<br />
GBRMANY<br />
Horst Albrecht<br />
Volkswagen AG<br />
Winfried Asmuth<br />
TUV Ithcinland<br />
Toshio Ban<br />
HondaR&DEurope<br />
Hartmut Burgr'r<br />
Volkswagen AG<br />
Bo Cavell<br />
Autoliv GmbH<br />
Horst Dalibor<br />
Volkswal5cn AG<br />
Karl Frcderick Dtsch<br />
Ministry of Transport<br />
fens Eberius<br />
Porsche AC<br />
Harald Eggelmann<br />
Mercedes-Bcnz AG<br />
Willi Elsenheimer<br />
Adam Opel AG<br />
Eberhard Faerber<br />
Federal Highway Research<br />
Institute<br />
Joerg Fcllerer<br />
Bayerische Motorcn Werke AG<br />
Detlef Frank<br />
Bayerische Motoren Warke AG<br />
Joachim Franz<br />
Siemens AC<br />
Bernd Fricdel<br />
Fcdcral Highway Research<br />
Institute<br />
Wol f-Richard Frielingsdorf<br />
Mercedes-Benz AC<br />
Klaus-Peter Clacser<br />
Federal Highway Research<br />
Institute<br />
furgen Grandel<br />
DEKI{A<br />
Johann Guggenberger<br />
Siemcns<br />
AC<br />
Josef Habcrl<br />
Bayerische Motoren Wc'rkc AC<br />
Hans Hagen<br />
Karl Kassbohrer Fahrzcu gwr-rke<br />
GmbH<br />
Lothar Hcider<br />
Mercedes-Bcnz AC<br />
Wolfram Hcll<br />
University Munich<br />
Thonras Humtncl<br />
HUK - Vc'rband<br />
Dirnitrios Kallieris<br />
U nivcrsity of Heidclbcrg<br />
Karl-Heinz Kartenberg<br />
Porsche AC<br />
Jorg Kerwath<br />
HondaR&DEuropc<br />
Kikuzo Kitaori<br />
Mitsubishi Motors Europe, B.V.<br />
]ucrgcn H. Kloeckncr<br />
BASt, Fcderal Highway Rcscarch<br />
Institute<br />
Hubert Koch<br />
Industrie Vcrband Motorr;rd<br />
Bernhard Koonen<br />
TUV Rheinland e.V.<br />
Gerald Krabbcl<br />
Tcclrnische Universitat Bcrlin<br />
Bcrnd Kraemer<br />
TLIV Rheinland c.V.<br />
Hans-Joachim Kraft<br />
Bayerische Motorcn Werke AG<br />
Heinz Kuncrt<br />
SEKUltlT4las Union GmbH<br />
Klaus Langwie'der<br />
HUK - Vcrband<br />
Bog-Soo Lc'e'<br />
Institute of Automobilcnginr'ering<br />
Heinz Lcffle'r<br />
Bayr:rischr' Motorcn Wcrkr' AC<br />
Herbcrt Loffelholz<br />
Fedcral Industry of Transport<br />
Horst4eorg Marks<br />
Volkswagen AC<br />
Cunther Menzel<br />
Volkswagcn AC<br />
Yoshimoto Nagamoto<br />
Mazda Motor Corp.<br />
Hiroyaki Nishioka<br />
Toyoda Cosci Co., Ltd.<br />
Michael Iropp<br />
Universitat der Bundeswehr<br />
Berud Itichtcr<br />
Vcrlkswagen AG<br />
Ernst-Rudiger Rohr<br />
Mcrccdcs-Benz AC<br />
Klaus Rompe<br />
TUV Ithcinland c'.V.<br />
Willibald Roth<br />
Kolbqrnschrnidt AC<br />
Dietcr Schaper<br />
Electrolux Autoliv<br />
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Thotnas Scharnhcrrst<br />
Volkswagcn l{csearch Forschung<br />
Fahrzeugtcchnik<br />
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Dit'tt'r Schcuncrt<br />
Mcrr-rxles-Benz AC<br />
Andrcas Schindler<br />
TUV Rhcinland e.V.<br />
Fricd rich-Karl Schlotterbcck<br />
Europcan Contponents<br />
Dcutschland<br />
Achirn Schmitz<br />
TUV lthcinland e.V.<br />
Gr'rhard Schontag<br />
Mcrr,:cdes-Br'nz AC<br />
Ruprecht Sinnhubc-r<br />
Volkswagcn AC<br />
Alcxarrtier Sporner<br />
HUK Verband<br />
,
Armin Starck<br />
DEKRA<br />
Hans-Eggert Tonnesen<br />
Ankrn Ellinghaus CmbH & Co. KG<br />
Hidcnori Uki<br />
Mitsubishi Motors Europe B.V.<br />
Hans-Josef Vasen<br />
Kolbenschmidt AC<br />
fesko Veenhuis<br />
Volkswagen AG<br />
Elmar Vollmer<br />
Audi AC<br />
Klaus Von Vcrsen<br />
Engineering Systems <strong>International</strong><br />
L,othar Wech<br />
T.U.V. Bayern eV.<br />
Hanns*Peter Weisbarth<br />
Bayerischc Motoren Werke AC<br />
Ulrich Wezel<br />
Porsche AC<br />
Frank Wolf<br />
Mercedes Benz AG<br />
Robert Zobel<br />
Volkswagcn AG<br />
IIUNGARY<br />
Csaba Siklos<br />
Ministry of Trafi sportation<br />
IRELAND<br />
Denis Wood<br />
Wood and Associates<br />
ISRAEL<br />
Ran Cohen<br />
A.D.A.<br />
ITALY<br />
Elisabetta Amici<br />
Centro Sviluppo Mayterial<br />
Pierluigi Ardoino<br />
Fiat Auto SpA - Centro Sicuarczza<br />
Andrea Bencdetto<br />
Fiat Auto SpA - Centro Sicurczza<br />
Dante Bigi<br />
Fiat Auto SpA - Centro Sicurczza<br />
iuscaglione<br />
Fiat Auto SpA - Centro Sicurczza<br />
Stefano Buscaglione<br />
Fiat Auto<br />
t.tssore<br />
Fiat Auto<br />
F. Fissore<br />
Fiat Auto SpA - Ccntro Sicurczza<br />
F. Fossati<br />
Fiat Auto SpA - Centro Sicurczza<br />
C. Lomonaco<br />
Ministero dc'i Trasporti<br />
Fabrizio Luccetti<br />
Fiat Auto SpA - Centro Sir-urrczza<br />
Lamberto Milani<br />
Italdesign<br />
Silvia Monticr-lli<br />
Fiat AutoSpA - Centro Sicurezza<br />
A. Pastorino<br />
Fiat Auto SpA - Centro Sicurezza<br />
Claudio Schinaia<br />
Ministr'ro dei Trasporti<br />
F. Zacchilli<br />
Ministero dci Trasporti<br />
JAPAN<br />
Akihiko Akiyama<br />
Honda R & D<br />
Kenji Araki<br />
Sumitomo Metal Industries, Ltd.<br />
Yoshinori Bo'da<br />
M.I.T.I.<br />
Mr. Clepkenn<br />
Nissan Motor Company, Ltd.<br />
Hidehiko Enomoto<br />
Hino Motors, Boxy Research<br />
& Development<br />
Naoto Fukushima<br />
Nissan Motor Company, Ltd.<br />
Satoshi Fukushinra<br />
Toyota Motor Corporation<br />
Kenichi Coto<br />
Japan Automobile Rcscarch<br />
Institute<br />
Takl.shi Harigae<br />
Japan Automobile Research<br />
Institute<br />
Anendees<br />
Kazuo Higrrchi<br />
Honda It & D, I2th Research<br />
Section<br />
Kaneo Hiramatsu<br />
Japan Automobile Itr-scarch<br />
Institutc<br />
Masaki Hitotsuya<br />
Fuiitsu Ten Ltd.<br />
Kiyoshi Honda<br />
Honda It&D, lzth Research Section<br />
Noritoshi Horigome<br />
Ministry of Transport<br />
Masaru lgarashi<br />
Suzuki Motor Corporation<br />
Haruyuki Ikesue<br />
NSK, Ltd.<br />
Nanrio lrie<br />
Nissan Motor ComPany, Ltd.<br />
Hirotoshi Ishikawa<br />
|apan Automobilc Rcsearch<br />
Institute<br />
Shin-ichi Ishiyama<br />
Toyota Central R & D Labs, Inc.<br />
Kciji Isoda<br />
Mitsubishi Motors Corporation<br />
Kazuyoshi Katou<br />
Toyota Motor Corporation<br />
Junichi Kishimoto<br />
Nippron Koki Co., Ltd.<br />
Toru Kiuchi<br />
Toyota Mtrtor Corporation<br />
Ikuya Kohayashi<br />
Fujitsu Tcn Ltd.<br />
Akira Koike'<br />
Hino Motors, Vehicle Rescarch<br />
& Exper,<br />
Norio Komoda<br />
Toyota Motor Corp. R&D Planning<br />
Yutaka Kondoh<br />
Toyota Motor Colporation<br />
Ichiro Kurawaki<br />
Yarnaha Mcrtor Co., Ltd.<br />
Keiji Kusaka<br />
Kawasaki Heavy Industrics, Ltd.<br />
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lSth lntemetlonal Technlcal ConferenCe On Experlmental Safety Vehleles<br />
Tohru Kuwahara<br />
Isrrzu Motors Limited<br />
Hiroyuki Matsumoto<br />
Maeda Motor Corporation<br />
Inukai Mitsuo<br />
Tokai Rika Co., Ltd.<br />
Toshihito Miyagawa<br />
Toyota Motor Corporation<br />
Kyoichi Miyazaki<br />
]apan Automobile Research<br />
Institute<br />
Yoshiyuki Mizuno<br />
Nissan Motor Co., Ltd.<br />
Itsuro Muramoto<br />
Nissan Motor Company, Ltd.<br />
Kosuke Nagao<br />
Ashimori Industry Co., Ltd.<br />
Kenji Nakagawa<br />
Toyobo Co., Ltd.<br />
Akihisa Nakamura<br />
I.A.T.S.S.<br />
Muneo Nishizawa<br />
Takata Corp.<br />
Hideo Obata<br />
CRC Researrh Institute Inc.<br />
Akihiro Ohtomo<br />
Mssan Motor Company, Ltd.<br />
Katsumi Oka<br />
Honda R&D, Tochigi Center<br />
Shinichi Sakamoto<br />
Suzuki Motor Corporation<br />
Toshiaki Sakurai<br />
Mitsubishi Motors Corporation<br />
Shouichi Sano<br />
Honda R&D Co., Ltd.<br />
Michihisa Sasonoi<br />
Suzuki Motor Corporation<br />
Kazuhiro Seki<br />
Honda R & D<br />
Katsuhiro Sekine<br />
Pyro Safety Device Co.<br />
Iichi Shingu<br />
Toyota Motor Corporation<br />
Teruhisa Sugita<br />
Takata Corp.<br />
Katsunobu Sumida<br />
Toyota Motor Corporation<br />
Norio Sumitomo<br />
Toyobo Co., Ltd.<br />
xii<br />
Keizo Suzuki<br />
Tokai Rika Co., Ltd.<br />
Moriyuki Taguchi<br />
Yamaha Motor Co., Ltd.<br />
Nobuhiko Takahashi<br />
Nissan Motor Company, Ltd.<br />
Hidm Takeda<br />
Takata Corporation<br />
Masatoshi Tanaka<br />
Daihatsu Motor Co.<br />
Toshi Tanaka<br />
Sensor Technology Co.<br />
Katsunori' Taneda<br />
fapan Automobile Research<br />
Institute<br />
Izumi Tokunaga<br />
Ministry of Transport<br />
Junii Tonomura<br />
Suzuki Motor Corporation<br />
Yutaka Tsukiji<br />
Mazda Motor Corporation<br />
Takahiro Tsuruga<br />
Toghigi R&D Center<br />
Hiroshi Ueno<br />
Nissan Motor Company, Ltd.<br />
Shuji Yamaguchi<br />
Toyota Motor Corporation<br />
Kuniaki Yamakuse<br />
Honda Motor Co., Ltd.<br />
Takenori Yamamoto<br />
Honda R&D., Ltd.<br />
Yugi Yokoya<br />
Toyota Mcrtor Corporation<br />
Hiroshi Yoshida<br />
Mitsubishi Motors CorPoration<br />
Keigo Yoshida<br />
HondaR&DCo..Ltd.<br />
KOREA<br />
Youngtai Choi<br />
Korea Auto. Test & Res. Instit.<br />
NETHERLANDS<br />
Anna Agter<br />
Ministry of Transport and Public<br />
Works<br />
Hans Ammerlaan<br />
Ministry of Transport<br />
Peter De Coo<br />
TNO Road Vehicles Research<br />
Institute<br />
Hans Driever<br />
TNO Road Vehiclcs Research<br />
lnstitute<br />
Hans Huijbc'rs<br />
Ministry of Transport<br />
Paul Jacobs<br />
Volvo Car BV<br />
Edgar ]anssen<br />
TNO Road Vehiclcs Research<br />
Institute<br />
Dirk l,andheer<br />
Eindhoven University of<br />
Technology<br />
Henk Lupker<br />
TNO l{oad Vehicles Rescarch<br />
Institute<br />
|aap Maartense<br />
Volvo Car BV<br />
Gerard Meekel<br />
Ministry of Transportation and<br />
Public Works<br />
Department of Road<br />
Transportation<br />
Yashishi Mizutani<br />
Tokai Rika Co., Ltd.<br />
John Nieboer<br />
TNO Road Vehicles Research<br />
Institute<br />
Joop Pauwelussen<br />
TNO Road Vehicles Research<br />
Institute<br />
Jan Paul Peters<br />
Yamaha Motor Europe N.V.<br />
Bernard Reys<br />
TNO Road Vehicles Research<br />
Institute<br />
Albert Roelfsema<br />
Volvo Car BV<br />
L.T.B. Van Kampen<br />
Institutc for I(oad Safetv Research<br />
Carla Van Moorsel<br />
Ministry of Transport<br />
]an Van Santen<br />
J.P.M. Van Santen Public Relations<br />
Fred Wegman<br />
Institute for Road Safety Research<br />
fac Wismans<br />
TNO Road Vehicles Research<br />
Institute
Willem Witteman<br />
Eindhoven University of<br />
Technology<br />
RUSSIA<br />
Serguei Efjmenko<br />
State Science and Technology<br />
Committee<br />
Anatolie Eiov<br />
City of Moscow<br />
Vladimir Federov<br />
Ministry of the Interior<br />
Vladimir Fedorov<br />
Inspection FAutomobiles de la<br />
Russie<br />
Evgenii Semenov<br />
Foundation for Road Safety<br />
Igor Vengerov<br />
S.T.C.E.C.<br />
Igor Vengueron<br />
Technical Center<br />
SPAIN<br />
favier Alvarez-Montalvo<br />
Ministry of Industry and<br />
Commerce<br />
Mercedes Menendez<br />
I.N.T.A.<br />
SWEDEN<br />
Rune Almquist<br />
Volvo Car Corporation<br />
Roger Alven<br />
Alvatec AB<br />
Sture Andersson<br />
Electrolux Autoliv<br />
Nils Bohlin<br />
Bohlin Consulting/Olstorp<br />
Per Branneby<br />
Saab Automobile AB<br />
Gustaf Celsing<br />
Autoliv Svenge AB<br />
Anders Eugennson<br />
Volvo Car Coryoration<br />
Erik Falk<br />
Volvo Car Cor?oration<br />
Lennart Fremling<br />
Swedish Road Safety Office<br />
L. Yngue Haland<br />
Electrolux Autoliv AB<br />
Soren Hedberg<br />
Swedish Road Safety Office<br />
|an Holmgren<br />
F.T.S.S.<br />
jan Ivarsson<br />
Volvo Car Corporation<br />
Goran Kahler<br />
Saab Automobile AB<br />
Janusz Kaizer<br />
Chalmers University of Technology<br />
Birgitta Kamren<br />
Folksam Research<br />
Magnus Koch<br />
Volvo Car Corporation<br />
Maria Koch<br />
Folksam Research<br />
Anders Kullgren<br />
Folksam Research<br />
Tony Landh<br />
Saab Automobile AB<br />
Kas Larsson<br />
Saab Automobile<br />
Stefan larsson<br />
Volvo Truck Corporation<br />
Thomas Lekander<br />
Swedish Road Safety Office<br />
Anders Lie<br />
Folksam Rcsearch<br />
Mats Lindquist<br />
Saab Automobile AB<br />
Per Lnvsund<br />
Chalmers University of Technology<br />
Biorn Lundell<br />
Volvo Car Corporation<br />
Fritz Hugo Martin Mellander<br />
Volvo Car Corporation<br />
Gert Nilson<br />
Chalmers University of Technolory<br />
Curt Nordgren<br />
Assoc. of Swedish Auto. Manuf.<br />
GIL)<br />
Hans Norin<br />
Volvo Car Corporation<br />
Anders Ohlund<br />
Volvo Car Coryoration<br />
Jan Olsson<br />
Autoliv Svenge AB<br />
Michael Persson<br />
Volvo Car Corporation<br />
Attendees<br />
fan Petzall<br />
Chalmers University of Technology<br />
Bengt Pipkorn<br />
Chalmcrs University of Technology<br />
Kare Rumar<br />
Swcdish Road & Traffic Res.<br />
Institute<br />
V,T.I.<br />
Lennart Strandberg<br />
Swedish Road & Traffic Res.<br />
lnstitute<br />
V.T.I.<br />
Mats Svensson<br />
Chalmers University of Tech ncrlogy<br />
Svcn-Erik Svensson<br />
Volvo Car Corporation<br />
Claes Tingvall<br />
Folksan'r Rcsearch<br />
Thomas Turbell<br />
Swedish Road & Traffic Research<br />
V.T.I.<br />
SWITZERLAND<br />
Robcrt Kaeser<br />
ETH Zurich<br />
Urs Maag<br />
University of Montreal<br />
Masahiko Naito<br />
Auto. Stand. lntemational Center<br />
Gottfried Treviranus<br />
Universtat Zurich<br />
Felix Walz<br />
Institute of Forensic Medicine<br />
UNITED KINGDOM<br />
Gordon Bacon<br />
M.I.R.A.<br />
John F. S. Bidgood<br />
RAC Motoring Services<br />
Philip Bly<br />
Transport & Roatl I{esearch<br />
Laboratory<br />
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13th lntemetlonel Technlcel Conterence on Experlmentel Satety Vehlcles<br />
Alan Bowker<br />
UK Transport Dep.-Vehicle<br />
Inspectorate<br />
feanne Breen<br />
PACTS<br />
David W, Burleigh<br />
Britax Excelsior Ltd.<br />
Bryan Chinn<br />
Transpnrt & Road Research<br />
Iaboratory<br />
Keith Clemo<br />
M.I.R.A.<br />
Laurcnce Clift<br />
ICE Ergomanics<br />
Anthony Denniss<br />
T.R.R.L.<br />
William H. Dixon<br />
Society of Motors Manufacturers<br />
& Traders<br />
Mark Dorn<br />
RSEL, Middlesex Polytechnic<br />
Eric Dunn<br />
Department of Transport<br />
Alan Dyche<br />
First Technolory Systems<br />
Nigel Earle<br />
Ford Motor Company, Ltd.<br />
Malcolm Eden<br />
Ford Motor Company, Ltd.<br />
Paul Fleming<br />
Breed Automotive<br />
Geoffrey Fletcher<br />
Ford Motor Company, Ltd.<br />
Alan Randell Giles<br />
Rover Croup, Ltd.<br />
K. Goense<br />
,A,irbags I nternational<br />
fohn Harris<br />
Transport & Road Research<br />
laboratory<br />
julian Hill<br />
University of Birmingham<br />
C. Adrian Hobbs<br />
Transport & Road Research<br />
Iaboratory<br />
Frederick |ohn Hope<br />
Hope Technical Developments,<br />
Ltd.<br />
)ohn Anthony Jeyes<br />
U.K. Department of Transport<br />
xiv<br />
Christophcr Kavanagh<br />
Airbags <strong>International</strong><br />
Douglas Kendall<br />
M.I.R.A.<br />
Michael lewis<br />
Rolls Royce Motors Ltd.<br />
Richard Lewis<br />
Ford Motqr Company, Ltd.<br />
Richard Lowne<br />
Transport & Road Research<br />
[,aboratory<br />
Murdoch Macaulay<br />
TRRL<br />
Murray Mackay<br />
University of Birmingham<br />
]ohn Miles<br />
Ove Arup and Partners<br />
Andrew Morris<br />
University of Birmingham<br />
Pat Murphy<br />
U.K. Dcpartment of Transportation<br />
Ian Douglas Neilson<br />
P.A.C.T.S.<br />
Robert Newton<br />
ICE Ergonomics<br />
Rock Nigel<br />
ICE Ergonomics<br />
Muir Parker<br />
First Technology Safety Systems<br />
Steve Parkin<br />
University of Birmingham<br />
Geoffrey Platten<br />
Ogle Design Ltd.<br />
Mostafa Rashidy<br />
Ford Motor Company, Ltd.<br />
Adrian Keith Roberts<br />
Transport & Road Rcsearch<br />
Laboratory<br />
Brian Robinson<br />
Transpot & Road Research<br />
Laboratory<br />
Peter Roy<br />
RSEL, Middle Polytc.chnic<br />
Majid Sadeghi<br />
Cranfield Impact Center<br />
Gcxrffrey Savage<br />
RSEL, Middlesex Polperhnic<br />
Petcr Victor Skuse<br />
Rover Croup, Ltd.<br />
Peter Slater<br />
Ford Motor Company, Ltd.<br />
Viv Stephens<br />
M.I.R.A.<br />
Richard Sturt<br />
Ove Arup and Partners<br />
Peter Thomas<br />
ICE Ergonomics<br />
S. Valkcnburg<br />
Airbags <strong>International</strong><br />
Rogcr Vingoc<br />
HW Structures Ltd.<br />
fohn Wall<br />
Transport & Road Rcsearch<br />
Laboratory<br />
Edmund Ward<br />
ICE Ergonomics<br />
Paul Wellicome<br />
M.I.R.A.<br />
Nigel Wemyss<br />
Ogle Design Ltd.<br />
Christopher Williams<br />
Ford Motor Company, Ltd.<br />
Christopher Withcrington<br />
RSEL, Middlesex Polytechnic<br />
UNITED STATES<br />
Steven Anderson<br />
ASL<br />
Kenichi Ando<br />
fetro New York<br />
Robert Arnold<br />
Motor Vehicle Manufacturers'<br />
Assoc.<br />
Robert A. Assunacao<br />
Morgan Melhuish et al.<br />
Thomas Baloga<br />
Mercedcs-Benz NA<br />
Douglas Bennett<br />
U.S. House of Representatives<br />
Barry Berson<br />
Hughes Aircraft<br />
Donald Bischoff<br />
NHTSA<br />
Russell Brantman<br />
Brecd Automotive<br />
Alex Butt<br />
Amcrican Suzuki Motor Corp.
Tercnce Chorba<br />
Centcrs for Disease Control - F36<br />
Carl Clark<br />
Safuty Systems Company<br />
Robcrt M. Clarke<br />
NHTSA<br />
Scott Cmper<br />
U.S. House of Represcntatives<br />
|erry Ralph Curry<br />
NHTSA<br />
Gregory Dana<br />
Association of <strong>International</strong> Auto.<br />
Manufacturers<br />
Robert Davcnport<br />
University of Zurich<br />
George Davis<br />
NHTSA<br />
Bruce Decker<br />
Toyota Motor Sales, U.S.A.<br />
Robert Denton<br />
Robert A. Denton. Inc.<br />
Kennerly H. Dgges<br />
University of Virginia<br />
fames Donovan<br />
Wilson, Elser, Moskowitz,<br />
Edelman, Dicker<br />
Deborah Ederer<br />
First Tcchnology Safety Systems<br />
William Randall Edwards<br />
Chrysler Corporation<br />
Karl-Heinz Faber<br />
Mercedes-Benz of North America<br />
Eugene Farber<br />
Ford Motor Co., Ltd.<br />
Michael Finkelstein<br />
Michael Finkelstein & Associates<br />
David Finnegan<br />
U.S, House of Representatives<br />
fohn Fleck<br />
J&JTechnologieslnc.<br />
Donald Frie
lgth ln,r,metlilnet Techntftel COnlerence on ExPerlmental Safety Vehicles<br />
David Romeo<br />
Romeo Engineering<br />
Anthony Sances<br />
Medical College of Wisconsin<br />
Albert Schlecter<br />
Chrysler Corporation<br />
Greg Schmeling<br />
Harley Davidson, Inc.<br />
Henry Seiff<br />
M.V.M.A.<br />
Tariq Shams<br />
G.E.S.A.C.<br />
William Shapiro<br />
Volvo Cars of Nofih America<br />
Philip Sheets<br />
Kawasaki Motors Corp., USA<br />
Philip Siracuse<br />
American Suzuki Motor Corp.<br />
Howard M. Smolkin<br />
NHTSA<br />
John Snider<br />
<strong>The</strong> University of Tennessee<br />
Douglas W. Toms<br />
Amc'rican Honda Motor Corp., Inc'<br />
Frank Turpin<br />
NHTSA<br />
fames Ughetta<br />
Wilson, Elser, Moskowitz,<br />
Edelman, Dicker<br />
Chris Von Will<br />
First Technology Safety SYstems<br />
William H" Walsh<br />
NHTSA<br />
Ronald Wasko<br />
Motor Vehicle Manufacturers'<br />
Association<br />
Emroy Watson<br />
Yamaha Motor Corp.<br />
Bill Weber<br />
Hughcs<br />
David Weir<br />
Dynamic Research, Inc.<br />
Marc Weiss<br />
Naval Biodynamics Lab<br />
Kenneth Yadvish<br />
Lester, Schwab, Kate & Dwyer<br />
Albert Yamada<br />
Masaoka & Assoc.<br />
Narayan Yoganandan<br />
Medical College of Wisconsin<br />
]ohn Zellner<br />
Dynamic Rescarch, Inc.<br />
Karl-Heiru Ziwica<br />
B.M.W.
Volume l. Opening Ceremonies Thru Session 5<br />
Contents<br />
Foreword<br />
Introduction<br />
Attendees<br />
SECTION 1. OPENING CEREMONIES<br />
Welcoming Address<br />
Jerry Curry, National Highway Traffic Safety Administration, Department of Transportation<br />
United States<br />
Keynote Address<br />
Jean-Michel Bernard, Minister of Delegation for Road Safety, Arche de la Defense<br />
France<br />
Awards Presentations<br />
Chairman: George L. Parker<br />
Awards for Safety EngineeringExcellence<br />
$pecial Awards of Appreciation<br />
SECTION 2. GOVERNMENT STATUS REPORTS<br />
Chairman: Howard M. Smolkin, United States<br />
Commission of the European Communities<br />
Daniel Verdiani, Directeur General, Direction and Generale III<br />
Karl-Friedrich Ditsch, Ministry of Transport<br />
fapan<br />
Noritoshi Horigome, Ministry of Transport<br />
Italy<br />
Franco Zacchilli, Ministero dei Trasporti<br />
Canada<br />
S. Christopher Wilson, Transport Canada<br />
<strong>The</strong> Netherlands<br />
Gerard Meekel, Ministry of Transportation and Public Works<br />
Sweden<br />
Lennart Fremling, Ministry of Transport<br />
iii<br />
v<br />
vii<br />
d<br />
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4<br />
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ii<br />
.<br />
.;<br />
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I :<br />
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10<br />
15<br />
17<br />
'17<br />
19<br />
23<br />
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lSth tnternatlonal Teehnlcel Conference on Experimental Safety Vehlcles<br />
United States<br />
George L. Parker, National Higliway Traffic Safety Adnrinistration<br />
France<br />
Ceorge Dobias, Institut National de Recherche sur les Transports et leur S6curit6<br />
SECTION 3. TECHNICAL SESSIONS<br />
Technical Session 1: Crash Investigation and Data Analysis<br />
Chairpersotr: Fred Weg;man, <strong>The</strong> Netherlatrds<br />
sl-o-02<br />
Advanced Accident Data Collection-Description and Potentials of a<br />
Comprehensive Data Collection System<br />
B. Kamren, M. v Koch, A. Kullgretr, A. Lie, A. Nygren, C. Tingvall<br />
Folksam Research and Chalnrers University of Technology<br />
5L'C-03<br />
Data Linkages in Real Crash Analysis; c: A Kpv Key fn to Proqress Progress in Road Safetv Safety .<br />
. . . 45<br />
Urs Maag, Denise Desjardins, Claire Laberge-Nadeau<br />
Universite de Montreal<br />
sI-o-04<br />
''<br />
Child Casualties in Fatal Car Crashes . . .<br />
" ' 48<br />
Harold Valee, Marie Christine Caiilieret, Gerard Faverjon, Jean Yves Le Coz,<br />
Jean Marie Heinrich, Christian Tl'ronras<br />
AcciderrtResearclrandBion1ecIratricsLaboratoryAssociatedwitlrPeugeot<br />
Jean Claude Coltat, Poissy Intercomnrllnal Hospital Centre<br />
Clar,rde Cot, Institute of Biomechanics and Accident Research<br />
Alain Patel, Orthopaeclic Research lnstitute<br />
s1-o-05<br />
Data Analysis of the Speed-Related Crash Issue<br />
' ' ' 57<br />
Noble Bowie, Marie Walz<br />
National Highway Traffic Safety Adnrinistration<br />
:<br />
sl-o-06<br />
CyclistsandPedestriansin<strong>The</strong>Netherlands:DifferentNeedsof IniuryProtection?... '...... 63<br />
L.T.B. van Kanlpen<br />
SWOV Institute for Road Safetv Research<br />
i<br />
s1-o-08<br />
<strong>The</strong> Cause of Head Iniuries in Real World Crashes<br />
67<br />
Pete Thon'ras, Mo Bradforc'l, Edmr-rnd Ward<br />
Research lnstitute for Corrsunrer Ergonomics, Loughborouglr University of Technology<br />
sI-o-09<br />
Car Model Safety Rating-Further Development Using the Paired Comparison Method . ' . . . . 78<br />
M. v Koch, A. Kullgren, A. Lie, C. Tingvall<br />
Folksanr Research and Chalnrers University of Technology<br />
sI-o-10<br />
Driver Fatality Risk in Two-Car Crashes: Dependerrce on Masses of Driven and Striking Car . . 83<br />
Leonard Evans, Michael C. Frick<br />
General Motors Research Laboratories<br />
xviii<br />
37<br />
41
sI-o-11<br />
A Collection of Recent Analyses of Vehicle Weight and Safety<br />
Terry M. Klein, Ellen Hertz, Sherry Borener<br />
National Highway Traffic Safety Administration<br />
s1.-o-12<br />
CompatibilityProblem3ofSmallandLargePassengerCarsinHeadonCollisions<br />
G. Ernst, E. Bnihning, K.P. Glaeser, M. Schmid<br />
Federal Highway Research<br />
Institute, BASI<br />
sl.-o-14<br />
Survey of Car-To-Fixed-Obstacle Fatal Crashes * r r,<br />
Claude Henry, Serge Koltchakian, Gdrard Faverjon, Jean<br />
lll<br />
yves Le Coz<br />
Iaboratory of Accident Research and Biomechanics Associated with Peugeot SAlRenault SA<br />
Alain Patel, Claude Cot<br />
Orthopaedic Research Instifute<br />
s1-w-16<br />
Patterns and Causes of Serious Iniury Amongst Car Occupants .<br />
Peter L. Harms<br />
Private Consultant<br />
l2l<br />
R.J. Tunbridge ' :<br />
Transport and Road Research l,aboratory<br />
s1-w-17<br />
:<br />
<strong>The</strong> Use of Crash Iniury Research Data by the Vehicle Inspectorate to Identify<br />
Secondary Safety Concerns<br />
Alan Bowker<br />
Department of Transport<br />
13d<br />
sl-w-19<br />
Air Bags in Crashes: Clinical Studies from Field Investigations<br />
Donald F. Huelke, Jamie L. Moore<br />
University of Michigan Transportation Research Institute<br />
]. Vernon Roberts<br />
National Highway Traffic Safety Administration<br />
sI-w-21<br />
<strong>The</strong> Incidence of Multiple Injuries in Motor vehicle crashes 14g<br />
Stephen Luchter, Ruth Isenberg<br />
National Highway Traffic Safety Administration<br />
sT-w-22<br />
Crash Data Plans for the United States<br />
William H. Walsh<br />
Na ti onal Hi ghway Tra ffi c Safety Administration<br />
sL-w24<br />
A Proposal for a Simplified Injury Scale "SAIS 9" for Use in Large Scale Accident Studies<br />
Felix Walz<br />
Institute of Forensic Medicine<br />
Klaus Langwieder<br />
office for Motor vehicle safety Research, HUK-Insurers' Association<br />
Contents<br />
140<br />
'162
lSth ,ntematlonel Technlcel Conference on ExPerlmentel Safety Vehlcles<br />
sL-w-25<br />
Various Aspects on Crashworthiness Calculations<br />
M. Igarashi, K. Nagai<br />
Suzuki Motor Corporation<br />
sl-w-26<br />
Crash Pulse Recorder (CPR)-Development and Evaluation of a Low Cost Device<br />
for Measuring Crash Pulse and Delta-V in Real Life Accidents .<br />
B. Aldman, A. Kullgren, A. Lie, C. Tingvall<br />
Folksam Research and Chalmers lJniversity of Technology<br />
sL-w-27<br />
An Overyiew of the Vehicle Inspectorate's Database on Bus, Coach and Goods Vehicle<br />
Examinations Following Maior Accidents<br />
Donald Macdonald<br />
Department of Transport Vehicle Inspectorate, Accidents, Defect and Recalls Branch<br />
sl-w-28<br />
A General Approach to Estimating Frontal Impact Collision Speeds<br />
Denis P. Wood<br />
Wood & Associates<br />
sl-w-29<br />
Special ProducUPerson CVS-ATB 3'D Simulations . . . .<br />
Donald Friedman<br />
Donald Friedman Liability Research Group<br />
l<br />
Technical Session 2l Safety Improvements<br />
from Advanced Vehicle/Highway Technology<br />
Chairperson: Claudio Schinaia, Italy<br />
s2-o41,<br />
Intelllgent Vehicle Highway Systems-safety Benefits and Public Policy<br />
Eugene I. Farber<br />
Ford Motor Company<br />
sz-o42<br />
Description of Three PROMETHEUS Demonstrators Having Fotential Safety Effects<br />
Daniel Jean Augello<br />
Renault Research Stafl PROMETHEUS Project Manager<br />
s}-o.{,3<br />
<strong>The</strong> First Practical Application of a Laser Radar Rear-end Collision Warning System<br />
in Production Heavy-duty Tmcks<br />
Itsuro Muramoto, Shigeru Okabayashi, Masao Sakata, Nissan Motor Co., Ltd.<br />
Tohru Yasuma, Kiyoshi Minami, Nissan Diesel Motor Co., Ltd'<br />
Todd Kohzu, Kansei Co., Ltd.<br />
s2-o44<br />
<strong>The</strong> Anti-Collision Radar in the DRIVE-SMILER Project . . .<br />
Pascal Deloof<br />
INRETS{RESTA<br />
Nathalie Haese, Paul Alain Rolland<br />
CHSUSTLFA<br />
181<br />
188<br />
192<br />
195<br />
199<br />
205<br />
209<br />
712<br />
?20
s2-o-}s<br />
Improved Active and Passive Safety by Using Active Lateral Dynamic Control<br />
and an lJnconventional Steering Unit .<br />
Per Briinneby, Bo Palmgren, Saab Automobile AB<br />
Anders Isaksson, Torbjcirn Pettersson, Mecel AB<br />
Stig Franz6n, Saab-scania AB<br />
s2-o46<br />
Contents<br />
Proposal for a Guidelin_e_ for Safety Related Elecbonics in Road Transport<br />
Systems (Drive Project V10S1)<br />
ryTltqd Asmuth, C. Heuser, H. Trier, 230<br />
J. Sonntag<br />
TUV Rheinland<br />
s2-o47<br />
Influence of Electromagnetic Fields Radiatedby Lighting Discharges<br />
on Automotive Electronic Components<br />
235<br />
S. Ficheux<br />
UTAC<br />
M. Klingler, M. Heddebaut<br />
INRETS<br />
s2-o48<br />
Improving Vehicle Safety Under Bad Weather<br />
Joop P. Pauwelussen<br />
TNO Road-Vehicles Research Institute<br />
sz-O-09<br />
Interactive Road Signalling-IslS<br />
246<br />
L. De Vaulx<br />
PSA Peugeot - Citroen<br />
s2-o-10<br />
Detection and conhol of the Degree of vigilance of Driverp . . z4g<br />
Michel Vallet, Sina Fakhar, Daniel Olivier, Daniel Baez<br />
InstitutNationaIdeRecherchesurIesTransportsetleurSecurit€<br />
sa-o-1.1.<br />
Technical and Medical rrl.rr Aspects rlspEfr$ Influencing rlrrruBnctng a Motorist's Mororrst-s Driving t-Jflvlng Ability ADtltty . . . . ; 256<br />
Andrea costanzo<br />
Rome University "La Sapienza"<br />
:<br />
Technical Session Bl Specialized Road Users<br />
Chairperson: Kenichi Coto, Japan<br />
Co-Chairperson: Kaneo Hirarnatsu, Japan<br />
s3-o41<br />
Factors that Influence the Involvement of Motorcycle Riders in Traffic Accidents<br />
Hubert Koch<br />
Industrie-Verband Motorrad Deutschland e. V.<br />
Ulrich Schulz<br />
Universitiit Bielefeld<br />
ss-o-02<br />
Computer Simulation of Motorcycle Airbag Systems<br />
I'J' Nieboer, A.P. Goudswaard, J. wismans, E.G. Janssen, A.c.M. versmissen<br />
TNO Crash-Safety Research Centre<br />
224<br />
??q i<br />
263<br />
268<br />
xxi<br />
i'i<br />
"T<br />
*<br />
,lj<br />
1<br />
I<br />
i<br />
;<br />
i'i<br />
:d<br />
iil<br />
it{<br />
+<br />
,i<br />
I<br />
;,1<br />
.ts<br />
ilrl<br />
ii<br />
:'d<br />
,1<br />
I1<br />
rj<br />
.l
13ffi lntematlonel Technlcal ConferenCe On Experlmental Satety Vehlcles<br />
s3-o-03<br />
<strong>The</strong> Effect of Dummy Leg Design on Motorcycle Crash Test Results . . . 273<br />
M.A. Macaulay<br />
Brunel University<br />
H. Karimi, B.P. Chinn<br />
Transport and Road Research Laboratory, Department of Transport<br />
s3-o45<br />
Cwrent Situation of Pedestrian Accidents and Researchinto<br />
Pedestrian Protection in fapan . . 281<br />
Hirotoshi Ishikawa, Kunio Yamazaki, Kosl-riro Ono<br />
Japan Automobile Research Institute, Inc.<br />
Akira Sasaki<br />
Japan Automobile Manufacturers Association<br />
s3-o-05<br />
Proposals for Test Methods to EvaluatePedeshian<br />
Protection for Cars 293<br />
]. Harris<br />
EEVC Working Croup'10 on PedestrianProtection<br />
s3-o-07<br />
Development of<br />
K.-P. Glaeser<br />
Federal Highway<br />
s3-o-08<br />
Subsystem Test for Peclestrian Lower Leg and Knee Protection .<br />
D. Cesari, F. Alotrzo, M. Matyjewski<br />
INRETS<br />
53-O-09<br />
Finite Element Modelling of Pedestrian Head Impact onto Automobile Hoods . . . . 317<br />
David R. Lemmon, Robert S. Ballinger, Ronald L. Httston<br />
Department of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati<br />
John Kessler, Jeff Elias, David Zuby<br />
Vehicle Research and Testing Center, Transportation Research Center of Ohio<br />
s3-o-1-0<br />
<strong>The</strong>EffectoftheVehicleShucture,sCharacteristicsonPedestrianBehavior<br />
Kazuo Higuchi, Akihiko Akiyama<br />
Honda R&D Co., Ltd.<br />
s3-o-12<br />
New Aspects for Optimizing Child Restraint Systemsl Experiences from Accidents,<br />
Trolley Tests and Interviews .<br />
K. Langwieder, Th. Hummel<br />
HUK-Verband<br />
s3-o-13<br />
Side Protection and Chitd Reshaints-Accident Data and Laboratory Test<br />
Including New Test Methods . . .-. .<br />
B. Kamr6n, A. Kullgren, A. Lie, B-4. Skdld, C. Tingvall<br />
Folksam Research and Chalmers lJniversity of Technology<br />
s3-o-17<br />
A Technical Evaluationof<br />
Motorcycle Leg Protectors<br />
Nicholas M. Rogers<br />
<strong>International</strong> MotorcycleManufacturers<br />
Association<br />
xxii<br />
a Head Impact Test Procedure for I'edestrian Protection 302<br />
Research Institute GASt)<br />
310<br />
330<br />
34r<br />
345
s3-w44<br />
Further crash rests of Motoreycle Leg protectors as proposed ln the<br />
UK Draft Specification . .<br />
Nicholas M. Rogers<br />
<strong>International</strong> Motorcycle Manufacturers Association<br />
Contents<br />
s3-w-16 l<br />
APR Proposals for Child Protection in Cars<br />
378<br />
Y. Pincemaille, F. Brun-Cassan, P. Caillibot, J-y. Le Coz<br />
Laboratory of Accidentology and Biomechanics Associated with Peugeot S.A. and Renault (ApR)<br />
G. Brutel<br />
P.S. A.-Peugeot-Citroen, [aboratory of Automotive Safety<br />
s3-tv-l8<br />
Initial Conclusions of an <strong>International</strong> Task Force on C'hild Restraining Systems<br />
385<br />
C. TarriEre, X. Trosseille<br />
Ddpartement des Sciencesde<br />
l'Environnement, Renault<br />
G. Carlsson<br />
Volvo Car Corporation<br />
s3-w-20<br />
wheelchair and occupant Restraint system For use In Buses 3gl<br />
Jan Petziill<br />
Chalmers University of Technology<br />
s3-w-22<br />
Bonnet Leadlng Edge Sub-systems Test for Cars to Assess Protection for Peclestrians . 402<br />
G.I.L. Lawrence, B.J. Hardy, J. Harris<br />
Transport and Road Research Iaboratory<br />
s3-w-23<br />
Inadequate Head and Neck Protection of Ctild Seats 473<br />
Donald Friedman<br />
Liability Research Group<br />
Technical Session 4; Safety Improvements<br />
from Advanced Vehicleillighway Technology<br />
Chairperson: Bernard Durand, France<br />
s4-o41,<br />
Driver Needs and Safety Effects of PROMETHEUS Functions<br />
H6lEne Fontaine, Gilles Malaterre<br />
Itutitut National de Recherche<br />
sur les Transports et leur sdcurit6<br />
s4-o42<br />
Impact of PROMETHEUS Functions on Traffic Safety<br />
|tirgen H. Klcickner<br />
Federal Highway Research Instihrte (BASt)<br />
s4-o43<br />
<strong>The</strong> NHTSA IVIIS Program for Enhancing Safety Through Crash Avoidance Improvement<br />
William A. Leasure, Jr.<br />
National Highway Traffic Safety Administration<br />
350<br />
4?.4
1}th ,ntemetlonel Technlcal ConferencC on Experimental Sefety Vehtcles<br />
s4-o44<br />
opportunitles in Automotive safety: A Public Health Perspective . . . .<br />
438<br />
David C. Viano<br />
General Motors Research laboratories<br />
Richard F. Davis, Milford R. Bennett, Robert L. LeFevre, Richard E. Rasmussen, Mitchel C. Scherba<br />
General Motors Corporation<br />
s4-o4s<br />
Safety Aspects of Driving with Intelligent Vehicles and Intelligent Traffic Systems<br />
449<br />
Dr.-Ing. Thomas Scharnhorst<br />
Volkswagen AG<br />
s4-o-06<br />
PSA Proiect'Tor A Safer Road"<br />
454<br />
J.P. Faidy, J. Hamon<br />
TTSA<br />
s4-o47<br />
Automated Vehicle/Highway System<br />
Norio Komoda, Keiji A;ki, Takaharu Saito, Takashi Shigematsu, Hidetoshi Ichikawa<br />
Toyota Motor Corporation<br />
s4-o48<br />
'COVER'<br />
Safety Synthesis Vehicle<br />
467<br />
Nelson Casadei<br />
Renault<br />
s4-o49<br />
Vehicle Safety in the 1990's<br />
. 472<br />
|ohn M. Leinonen<br />
Ford Motor Company<br />
s4-o-10<br />
Guiding Drivers through a Mehopolis: Traffic Safety Aspects of the Guidance and<br />
Informition System ge-rtin (LISBi<br />
479<br />
M.M. Popp, B. Farber, A. Schmitz<br />
University of the Armed Forces<br />
s+w-11,<br />
Collision Avoidance-Function Allocation to Humans and/or Machines<br />
482<br />
G. Reichart<br />
BMW AG<br />
s+w-1.s<br />
Ftom Accidentology Analysis to the Intelligent Vehicle . . .<br />
487<br />
J.P. Colinot<br />
PSA Peugeot - Citroen<br />
D. Lechner<br />
INRETS<br />
s4-w-16<br />
Conhol Station for Moving Car<br />
494<br />
A. Clerc<br />
INRETS<br />
s4-w-17<br />
Analysis of EOG and EEG Signals to Detect Lapses of Alertness in Car Driving Simulation . . 499<br />
S. Planque, D. Chaput, C. Petit, C. TarriEre, C. Chabanon<br />
Renault<br />
xxlv
s5-o41<br />
Technical Session 5: Side Impact Occupant Protection<br />
Chairperson: Richarc-l Lowne, United Kingdom<br />
Co-Chairperson: Ian Neilson, United Kingdom<br />
Analysis of Dummy Readings Affected by Secondary Impact Point Intensity<br />
Gontents<br />
in Side Impact Tests 5U5<br />
Tatsumasa Okamoto, Nobuhiko Takahashi<br />
Nissan Motor Co., Ltd.<br />
' '<br />
s5-o{3<br />
<strong>The</strong> Effect of Door Shucture on Occupant Iniury in Side Impact 509<br />
Hiroyuki Matsumoto, Hideaki Tanaka<br />
Mazda Motor Corporation<br />
s5-o44<br />
Protection of Ocnrpants Against Side lmpact<br />
Albert I. King, Yue Huang, John M. Cavanaugh<br />
Wayne State University<br />
55-O46<br />
<strong>The</strong> Protective Effect of Airbags and Padding in Side Impacts-Evaluation by a New<br />
Subsystem Test Method . . 523<br />
Yngve HAland<br />
Electrolux Autoliv AB<br />
Bengt Pipkorn<br />
;li;*<br />
urriversity of rechnology<br />
Air Bag System for Side Impact Occupant Protection 533<br />
Toru Kiuchi, Kenji Ogata, Toyota Motor Corporation<br />
Charles Y. Warner, Collision Safety Engineering<br />
John Jay Gordon, GMH Engineering<br />
s5-o-1.0<br />
"Renault VSS" Safety Vehicle; Occupant Safety in Side Impacts 542<br />
j. Rio, D. Pouget, N. Casadei<br />
Renault<br />
s5-o-17<br />
Parametsic Study on the Side Impact Simulation of Renault VSS 549<br />
C. Steyer, R. Najcharrs<br />
Renault<br />
s5-o-13<br />
A Simutation Method of Vehicte Model Coupling with Dummy in Slde Impact 555<br />
Yutaka Tsukiji, Koji Taga<br />
Mazda Motor Corporation<br />
s5-o-1.4<br />
A Resolutlon of Side Impact Phenomena by Means of Dynamic Nonlinear FEM Simulation<br />
and a Study of Vehicle Body Construction . . 560<br />
Akihiko Inagaki, Nobuhiko Takahashi, Akira Tohyama, Akihiro Ohtomo<br />
Nissan Motor Co., Ltd.<br />
1l .4<br />
j<br />
ii<br />
'fi<br />
fl r1<br />
|.<br />
.E<br />
,i<br />
.E<br />
il<br />
'j<br />
:<br />
ii<br />
,f<br />
L;<br />
j jl<br />
:.<br />
:4<br />
q<br />
i<br />
'd<br />
. 1<br />
T<br />
..'f<br />
:E<br />
:t<br />
1<br />
JT<br />
r;<br />
''4<br />
:x<br />
xxv .: il j<br />
-s<br />
j
1fith lnternatlonal Technlcal Conference on Exqerimental Satety Vehicles<br />
s5-o-15<br />
Results of MVMA Full Vehicle Side Impact Tests on 1990 Model Year Pontiac 6000 Vehicles<br />
Using BioSID and SID<br />
Ronald |. Wasko, Motor Vehicle Manufacturers Association<br />
Kenneth L. Campbell, University of Michigan Transportation Research Institute<br />
Sherman E. Henson, Ford Motor Company<br />
s5-o-16<br />
Comparative Performance of SID, BIOSID, and EUROSID in Lateral, Pendulum, Sled,<br />
and Car Impacts<br />
Joseph N. Kanianthra, Donald T. Willke, Hampton C. Gabler<br />
National Highway Traffic Safety Administration<br />
David S. Zuby<br />
TRC Inc.<br />
s5-o-17<br />
Influence of Test Procedure Characteristics on the Severity During Side Impacts ' . 588<br />
J.A. Bloch, D. Cesari, R. Zac<br />
INRETS<br />
s5-o-18<br />
A Simple Side Impact Test Method for Evaluating Vehicle Paddings and Side Structures . . . . 592<br />
Mats Lindquist<br />
Saab Automobile AB<br />
55-0-19<br />
A Dynamic Test Method for a Ca/s Interior Side Impact Performance<br />
598<br />
Anders Ohlund, Venti Saslecov<br />
Volvo Car Corporation<br />
s5-o-20<br />
Door Impact Test Procedure and Crush Characteristics for Side Impact Occupant Protection ' . 609<br />
Satoshi Fukushima, Shuji Yamaguchi, Tomoyuki Fukatsu, Kenichi Asano<br />
Toyota Motor Corporation :<br />
ss-o-21<br />
Crash-Rate and Door'Padding Effects in Side Impact Simulations . . . . 515<br />
Ran Cohen<br />
Armament Development Authority<br />
Edwin M. Sieveka, Walter D. Pilkey<br />
University of Virginia<br />
ss-o-22<br />
Evolution and Current Stateof<br />
Development of the Computer-Contolled<br />
Composite Test Procedure<br />
62t<br />
B. Richter<br />
ACEA/]AMA/MVMA<br />
s5-o-23<br />
Current Status of Correlation Between CTP and FST 634<br />
Shuji Yamaguchi<br />
Japan Automobile Manufacturers Association Inc.<br />
Katsunori Taneda<br />
Japan Automobile Research Institute Inc.<br />
xxvi<br />
567<br />
573
s5-o-24<br />
Future Enhancements of the Computer Conbolled Composite Test Procedure (CC-CTP) 646<br />
Ronald J. Wasko<br />
Motor Vehicle Manufacturers Association<br />
ss-o-25<br />
Simulation Model for Vehicle Perfornrance Improvement in Lateral Collisions . . . . ; 663<br />
P.J.A.de Coo, E.C. Janssen, A.P. Goudswaard, j. Wismaru<br />
TNO Crash-Safety Research Centre<br />
M. Rashidy<br />
Ford Motor Company<br />
ss-o-26<br />
<strong>The</strong> Development of a Method for Dynamic Simulation of Side Impacts<br />
Using a HyGe Accelerator-<strong>The</strong> S.I.D.E. Procedure<br />
668<br />
V.M. Stephens, D.G.C. Bacon<br />
Motor Industry Research Association<br />
s|-o-27<br />
Light Truck Side Impacts with Serious Occupant Iniury<br />
673<br />
Susan C. Partyka<br />
National Highway Traffic Safety Administration<br />
ss-o-28<br />
Development of the MIRA Free-Flight Headform Rig to Simulate Occupant Side-Impact<br />
and Pedestrian Impacts<br />
684<br />
K'c' clemo<br />
Motor Industry Research .^-*L Association<br />
A--^*:-li^-<br />
ss-w-29<br />
Experience of Using EUROSID-I in Car Side Impacts<br />
M.C. Beusenberg, E.C. Janssen, TNO Crash-Safety Research Centre<br />
R. Lowne, A. Roberts, Transport and Road Research krboratory<br />
K.-P. Glaeser, Bundesanstalt ftir Strassenwesen<br />
D. Cesari, INRETS<br />
s5-w-30<br />
Fatally Iniured Occupants in Side Impact Crashes 7L)l<br />
Diane C. Lestina<br />
In^surance Institute for Highway Safety<br />
Peter F. Cloyns, Stephen J. Rattenbury<br />
Vehicle Safety Consultants, Ltd.<br />
55-W-31<br />
Side Impact Into a Fixed Obiech What is at Stake? . . . . . 707<br />
Mouloud Haddak, Michelle Ramet, Gilles Vallet, Donrinique Cesari<br />
INRETS<br />
55-W-32<br />
ReshainedoccupantsontheNon-StruckSideinLateralCollisions<br />
G.M. Mackay, I. Hill, S. Parkin,I.A.R. Munns<br />
<strong>The</strong> University of Birmingham<br />
'<br />
590<br />
xxvll
Volume 2. Session 6 Thru Session 10<br />
Contents<br />
SECTION 3. TECHNICAL SESSIONS (CONTINUED)<br />
s6-o41<br />
Pivotal Characterization of Car Rollovers<br />
A.C. Malliaris, J. H. DeBlois<br />
DeBlois Associates, Inc.<br />
Technical Session 6: Light Vehicle Rollover<br />
Chairperson: William Leasure, United States<br />
s6-045<br />
Analysis of the Factors Which Influence Rollover Crash Severity<br />
K. Digges, S. Klisch<br />
University of Virginia<br />
s6-o.{i6<br />
Manufacture/s Overview of Rollover Resistance Test Technology . . . . ;<br />
Robert L. LeFewe, Richard E. Rasmussen<br />
General Motors Corporation<br />
s6-o48<br />
<strong>The</strong> Urban Rolloven Characteristics, Iniuries, Seat-Belts and Eiection<br />
G.M. ldackay, S. Parkin, A.P. Morris, R.N. Brown<br />
Accident Research Unit, University of Birmingham<br />
s6-o-10 ;<br />
Study on Passenger Car Rollover Simulation 747<br />
Toshiaki Sakurai, Yoshiharu Takigawa, Hitoshi Ikeno<br />
Mitsubishi Motors Co., Ltd.<br />
s6-o-17<br />
Roof Collapse and the Risk of Severe Head and Neck Iniury . 753<br />
Donald Friedman, Keith D. Friedman<br />
Liability Research Group<br />
s6-w-1.2<br />
Effect of Car Size on the Frequency and Severity of Rollover Crashes . ; . . . 765<br />
Charles ]. Kahane<br />
National Highway Traffic Safety Administration<br />
xxvru<br />
721<br />
733<br />
747
'<br />
Technical Session 7: Crash Avoidance Research<br />
Chairperson: Kare Rumar, Sweden<br />
s7-o41<br />
WheelsAnti-LockSystemsforBigSeriesPassengerCars.<br />
P. Brun<br />
[lSA Peugeot - Citroen<br />
s7-o42<br />
Improvement$ in Active Safety by Innovation for Automatic Stability Control Systems<br />
Dr.-Ing. Heinz Leffler<br />
BMW AG<br />
s7-o43<br />
Traction Conhol Technology for Improved Driving Safety<br />
Hiroshi Yoshida, Tadao Tanaka, Keiji Isoda, Koichi Kamiya<br />
Mitsubishi Motors Corporation<br />
s7-o44<br />
Controlled Suspension for Better Safety<br />
]mn-Pascal Reille, Charles Blanot<br />
Renault Direction des Etudes<br />
s7-o4s<br />
Improvement in High-Speed Safety Through Active Suspension Conhol<br />
Naoto Fukushima, Namio Irie<br />
Nissan Motor Co., Ltd.<br />
s7-046<br />
Development of Tyre Checking Equipment<br />
Roland Lucquiaud<br />
U.T.A.C.<br />
57-O47<br />
How About the Average Driver in a Critical Situation? Can He Really Be Helped<br />
by Primary Safety Improvements? .<br />
Alain Priez, Institut de Recherche Anatamo-Chirurgical et de Biomecanique Appliqu6e<br />
Claire Petit, Irutitut de Recherche Biom6canique et Accidentologique<br />
Bruno Gu6zard, Lionel Boulommier, Association d'Aide i la Recherche int6ressant<br />
la M6decine du Travail<br />
Andr6 Dittmar, Alain Delhomme, Laoratoire de <strong>The</strong>rmoregr.rlation CNRS URA<br />
Evelyne Vernet-Maury, Universitd C. Bernard<br />
Edwidge Pailhous, Psychologist, 82 bd. Buzenval, Paris<br />
fean-Yves Foret-Bruno, Claude Tarriere, Renault France<br />
s7-o48<br />
Crash Avoidance Capabitity of 50 Driv€rs in Different Cars on Ice . .<br />
Lennart Strandberg<br />
Swedish Road and Traffic Research Instihrte, VTI<br />
s7-o-10<br />
Simulation as a Design Aid<br />
E. Cirardot, P. Tardivon<br />
IISA Peugeot-Citroen<br />
Contents<br />
-<br />
784<br />
7W<br />
794<br />
805<br />
810<br />
826
lSth lnternatlonel Teehnlcel Conference on Experimental Sefety Vehlcles<br />
s7-o,11<br />
Analysis of Accidents in Right Turns Using aFvzzy Logic Simulation Model 830<br />
Hiroshi lJeno, Kiyoshi Ochiai<br />
Nissan Motor Co., Ltd.<br />
Technical Session 8: Biomechanics and Dummy Development<br />
Chairperson: Dominique Cesari, France<br />
s8-o41<br />
EvaluationofImpactResponsesoftheEURoSID.1andBIoSID<br />
Takeshi Harigae, Koji Ohsaki, Haruo Ohmae<br />
]apan Automobile Research Institute, Inc.<br />
Tatsumasa Okamoto, Masayoshi Hayashida<br />
Japan Automobile Manufacturers Association, Inc.<br />
s$-o-02<br />
<strong>The</strong> Biofidelity of the Production Version of the European Side Impact Dummy<br />
"EUROSID.I'<br />
..<br />
A.K. Roberts, M. Beusenberg, D. Cesari, K-P. Glaeser<br />
European Experimental Vehicles Committe+Working Group 9<br />
s8-o{3<br />
A Comparison of Hybrid III and Cadaver Thorax Response Under Diagonal Belt Loading<br />
Sedn 6 Riorddin, Michelle Ramet, Dominique Cesari, Robert Bouquet<br />
INRETS<br />
s8-o44<br />
<strong>The</strong> Use of a Multi-Accelerometric Method in Automotive Safety Tests<br />
L. Oudenard, F. Bendjellal, A. Bellini, J. Uriot<br />
Peugeot 5.A./Renault<br />
s8-o{5<br />
EUROSID I and BIOSID Impact Response Characteristics vs. ISO Biofidelity Requirements<br />
F. Bendjellal, G. Fuld, E. Hautmann, M. Koch, H. Marks, A' Pastorino<br />
ACEA Working Group on Dummies<br />
s|-o45<br />
Scaling HYBRID III and Human Head Kinematic Responses to Frontal Impact<br />
Marc S. Weiss, Sal Guccione<br />
Naval Biodynamics l,aboratory<br />
Terry A. Watkins<br />
University of New Orleans<br />
s8-o{)7<br />
Facial Fracture Probability Secondary to Steering Wheel Impact<br />
Narayan Yoganandan, Anthony Sances, Jr., Frank Pintar, John Reinartz<br />
Medical College of Wisconsin<br />
Mark Haffner<br />
National Highway Traffic Safety Administration<br />
s8-o49<br />
An Improved Finite Element Model of the Human Thorax<br />
Gordon R. Plank<br />
Volpe National Transportation Systems Center<br />
nof H. Eppinger<br />
National Highway Traffic Safety Administration<br />
xxx<br />
850<br />
860<br />
862<br />
87'l<br />
887<br />
891<br />
902
s8-o-1.0<br />
Analytical Trauma Research Using the Chest Band<br />
Nopporn Khaewpong<br />
Chi Associates, [nc.<br />
Rolf H. Eppinger, Richard M. Morgan<br />
National Highway Traffic Safety Ad ministration<br />
s8-o-11<br />
3-D Anatomic Brain Model for Relating Cortical Sbains to Automobile Crash Loacting<br />
F. Dimasi<br />
Volpe National Transportation Systems Center<br />
J. Marcus, R. Eppinger<br />
National Highway Traffic Safety Administration<br />
s8-o-1.2<br />
Dynamic Studies with Chest Contours<br />
David Skrade, Narayan Yoganandan, Anthony Sances, jr., ]ohn Reinartz, Frank Pintar<br />
Medical College of Wisconsin<br />
s8-o-14<br />
Crash Tests-One Element to Assess Passive Safety of Passenger Cars<br />
A. Schmitz, B. Kraemer<br />
TUV Rheinland e.V., Institute of Traffic Safety<br />
s8-w-15<br />
Analysis Method for External Forces Acting on the Dummy<br />
Koushi Kumagai, Fumio Matsuoka, Hiroyuki Takahashi<br />
Toyota Motor Corporation<br />
s8-w-1,6<br />
Brain Tolerance ln the Frequenry Field .<br />
R. Willinger, D. C6sari<br />
INRETS-LCB<br />
C.M. Kopp<br />
,.<br />
I<br />
s8-w-1.7<br />
M F S . : . :<br />
Development of a Sternum Displacement Sensing System for Hybrid III Dummy . . .<br />
Kenji Ogata, Masakazu Chiba<br />
Toyota Motor Corporation<br />
Hisashi Kawai, Fumio Asakura<br />
Nippon Soken, Inc.<br />
s8-w-18<br />
Test Procedures for Defining Biofidelity Targets for Lateral Impact Test Dummies<br />
A.K. Roberts, R.W. Lowne, M. Beusenberg, D. Cesari<br />
European Experimental Vehicles Committe-Working Croup 9<br />
s8-w-L9<br />
Influence of the Seat and Head Rest Stiffness on the Risk of Cervical Injuries<br />
in Rear Impact<br />
].Y. Foret-Bruno, F. Dauvilliers, C. Tarriere, P. Mack<br />
Renault<br />
s8-w-20<br />
Improvements in the ATB/CVS Body Dynamics Model<br />
John T. Fleck<br />
J&JTechnologieslnc.<br />
:.<br />
contents<br />
907<br />
.916<br />
924<br />
940<br />
947<br />
955<br />
968<br />
974
lgth tntematlonal Technlcat Conference on Expeilmental Safety Vehicles<br />
Technical Session 9: Frontal Crash Protection<br />
Chairperson: S. Christopher Wilson, Canada<br />
s9-o41<br />
Influence of Rigid Wall Impact Speed on Dummy and Vehicle Loadings<br />
Eberhard Faerber<br />
Federal Highway Research lnstitute (BAS0<br />
s9-o42<br />
Full Size Semi-Frontal Crash Simulations with Passenger Cars at 55 km/h<br />
Against Rigid Barrier<br />
Florian Schueler<br />
Insitute for Forensic Medicine, IJniversity of Heidelberg<br />
Peter Hupfer, Lothar Wech<br />
TW BAYERN<br />
59-0{3<br />
t rmnert<br />
Test Procedure Comparison in Frontal Impact<br />
Gilles Vallet, Dominique Cesari, Yves Derrien, SeAn 6 Riorddin<br />
INRETS<br />
s9-o44<br />
<strong>The</strong> Effects of FMVSS No. 208 and NCAP on Safety as Determined<br />
from Crash Test Results ' . .<br />
James R. Hackney<br />
National Highway Traffic Safety Administration<br />
s9-o{5<br />
Avoiding Sub-optimized Occupant Safety by Multiple_Speed Imp3ct Testing 1021<br />
Hans Norin, Clai ]ernstrcim, Magnus Koch, Stephan Ryrberg, Sven-Erik Svensson<br />
Volvo Car Corporation<br />
sg-o46<br />
Improving the Protection of Restsained Front $eat Occupants in Frontal Crashes<br />
7027<br />
D.J. Dalmotas, E.R. Welbourne<br />
Transport Canada<br />
s9-o47<br />
Upper Interior Head Impacts; <strong>The</strong> Safety Performance of Passenser Vehicles ' . 1037<br />
Hampton C. Gabler, Donald T. WiIIke<br />
National Highway Traffic Safety Administration<br />
J. joseph Wagner<br />
Automated Sciences Group, Inc.<br />
s9-o48<br />
A Study of the Safety Performance of Production Vehicles Equipped with Driver Air Bags<br />
in the NHTSA Test Programs<br />
William T. Hollowell, Fabienne J. Frey<br />
National Highway Traffic Safety Administration<br />
s9-o{9<br />
Supplemental Air Bag Restraint Systems: Successes and Challenges<br />
Robert H. Munson, Joseph C. Marsh<br />
Ford Motor Company<br />
977<br />
986<br />
988<br />
993<br />
1047<br />
1054
s9-o-10<br />
, Content$<br />
Seat Belt Pretensioners to Avoid the Risk of Submarining-A Study of Lap-Belt<br />
Slippage Factors 1060<br />
Yngve Hdland<br />
Electrolux Autoliv AB<br />
Gert Nilson<br />
Chalmers University of Technology<br />
sg-o-l1<br />
A Preliminary Field Analysis of Chryster Driver Airbag Effectiveness 1068<br />
W. Randall Edwards<br />
Chrysler Corporation<br />
s9-o-12<br />
<strong>The</strong> Need for Improved Shuctural Integrity in Frontal Car Impacts . . . 1073<br />
C. Adrian Hobbs<br />
Transport and Road Research Iaboratory<br />
59-O-13<br />
FrontalImpactProtectionRequiresaWholeSafetySystemIntegration<br />
C. Tarriere, C. Thomas, X. Trosseille<br />
Renault<br />
s9-o-14<br />
Occupant Protection in Coaches 1088<br />
Ross Dal Nevo, Paul Duignan, Michael Criffiths<br />
Roads and Traffic Authority of NSW<br />
s9-o-15<br />
Are Air Bags Compatibte with ChitA Reshaint Systems and Roadside Safety Features? 1095<br />
Thomas Turbell<br />
Swedish Road and Traffic Research Instifute, VTI<br />
s9-o-16<br />
Enhanced Airbag Model for the ATB Program 1098<br />
Tariq Shams, Nagarajan ltangaraj.en<br />
GESAC,<br />
Inc. .<br />
s9-0-L8<br />
Finite Element Simulation of Airbag Deployment and Interactions With an Occupant Model<br />
Using DYNASD 1103<br />
T.B. Khalil, General Motors Corporation<br />
R.J. Wasko, Motor Vehicle Manufacturers Association of the U.S.A.<br />
|.O. Hallquist, D.I. Stillman, Livermore Software Technology Corporation<br />
s9-o-19<br />
ModellingtheoccupantinaVehicleContext-AnIntegratec|Approach'..<br />
R.M.V. Sturt, B.D. Walker, J.C. Miles<br />
Ove Arup & Partners<br />
A. Giles, N. Grew<br />
Rover Group Limited<br />
sg-o-20<br />
Advances in Problem-Adaptive Occupant Modelling with PAM-SAFE 1121<br />
X. Ni, D. lasry, E. Haug<br />
Engineering Systems <strong>International</strong> S.A<br />
R' Hoffmann<br />
Engineering System r Tnfamrrinnrr <strong>International</strong> crrh GmbH<br />
'<br />
xxxiii<br />
::lI<br />
'li<br />
.,<br />
t{<br />
ri<br />
i<br />
ii<br />
:<br />
f il<br />
;<br />
*<br />
{<br />
_<br />
I<br />
.iE<br />
.i<br />
I<br />
1<br />
I<br />
4<br />
'I<br />
i<br />
.i<br />
!
lSth lnternatlonal TeChnlcal Conference on Experlmentdl Safety Vehicles<br />
sg-o-21.<br />
Design Considerations of the Passenger Airbag System<br />
1127<br />
Kazuhiro Seki, Kanichi Fukuda, Kiyoshi Honda<br />
Honda R&D Co., Ltd.<br />
sg-o-22<br />
Achievable Optimum Crash Pulses for Compartrnent Sensing and Airbag Performance . . . . . 1134<br />
Russel Brantman<br />
Breed Automotiv<br />
sg-o-23<br />
<strong>The</strong> MADYI\,IO Finite Element Airbag Model<br />
1139<br />
H.A. Lupker, H.B. Helleman, E. Fraternran, J. Wismans<br />
TNO Road-Vehicles Research Institute<br />
sg-o-25<br />
<strong>The</strong> Development of a Computer Program to Enhance the Fit of Seat Belts . 1147<br />
Doug Kendall<br />
Crash Protection Cenhe, Motor Industry Research Association<br />
sg-w-77<br />
Validation and Descriptlon of "PASSIM-PLUS" Passenger Airbag Model ' 1151<br />
Michael U. Fitzpatrick, Kelly E. Thompson<br />
Fitzpatrick Engineering<br />
s9-w-26<br />
Performance Evaluation of Crash Test Data Acquisition Systems<br />
Randa Radwan<br />
National Highway Traffic Safety Adn'rinistration<br />
fohn Nickles<br />
Research and Special Programs Administration, U.S. Department of Transportation<br />
s9-w-27<br />
New Technique Used by P.S.A, for Creating Dynamic Test Apparatus<br />
EnablingCraihSimulationinAccordancewithProgrammedLaws<br />
G. Mauron, F. Bocaly, F. Laurent<br />
IISA Peugeot - Citroen<br />
A. DepreFBixio, A. Grenier<br />
Domange-Jarret<br />
7757<br />
s9-w-29<br />
A New Compact Ewopean Drivet Airbag System<br />
1776<br />
Michel Kozyreff<br />
Autoliv Klippan<br />
Dieter Schaper :<br />
Autoliv GmbH<br />
s9-w-31<br />
Overlap Car-to-Car Tests Compared to Car-to-Half Barrier and Car-to-Full Barrier Tests 1180<br />
Carl Ragland, Gayle Dalrymple<br />
National Highway Traffic Safety Administration<br />
sg-w-32<br />
COVER: "Renault VSS' Safety Vehicle Frontal and Rear Impact Occupant Protection 1186<br />
G. Walfisch, D. Pouget, N. Casadei<br />
Renault<br />
xxxtv
l1#"'5 ty Packa gin g f or crashworth i n ess Perf orm ance<br />
P.ti. Sluse, N.D' Grew<br />
Rover GrouP Limited<br />
s9-W^35 r n^*rir*itra Prot€B$<br />
;';;;;"g Rear Seat Safety-A Continuins Prccess ' ' '<br />
Biiirn Lundell, c *J. c""l#;P J;; ili;; o fr ' ruritr''u *l Persso n' ca milla<br />
Volvo Car CorPoration<br />
tJ"#a'i<br />
Lap Belt in the n*"'i*i.Te Position save Human<br />
Lives?....<br />
Rygaard<br />
i.;. il;G'*n:, ! Ji*l:::.1i:^i:I<br />
Ll##lJ# tr ;d iF***'*:H: T:,:' ilil'J[::<br />
hSff l3lli,f;;r31'q:j,^***::S,-iiJ'-etM€tiers<br />
X, "?1i'1 illd; l; C;h.'ches orthopediques<br />
et Accidentologiques<br />
59-W-3S ..-- r|.a Dorfntrnrnce of Framed Ctild Seats Anchored by Adult Belts<br />
irt""i**ts Af fecting the Perfornrance<br />
M.R. Dorn, A'P' RoY<br />
rraiJor*t** Pol Ytechrric<br />
R.W.Lowne - , r-r^^--l<br />
t#sii* uno noua Research laboratorY<br />
59-W-39<br />
As; ;;u'-d, c'-":h,: 1 *11,-,:-lt:<br />
if;lilisgl,Y:.ll:t"fJ,ltl'LT*r*<br />
ilil ;"J'iiaf fic AuthoritY of<br />
Activation at Low Thresholcl Test Speed<br />
s9-w4o<br />
rations in Air Bag sensor<br />
Structural Conside<br />
Satnson<br />
Matthew Huang. ualsundru Green' Frederick<br />
Ford Motor ComPanY<br />
s9-w42<br />
Apprication of New Elastic_plastic-Brittle Materiar Models to composite crash simulation<br />
lnternati..ar s'A'<br />
E. Haug, o. Fort, i: Mii;;' n<br />
sftt*n''s<br />
1'1*J;:;'t;;'t^;'i'''g<br />
i;'w;il";be, I' Nakada' ToNEN corporation<br />
;: K#;T;;il,-ESI-APG<br />
?:;Trfrt*",ion of Automobile structural characteristics from Barrier crash rests<br />
eilif"td C' Chou' Yun S' Lin<br />
foia f.rrotor ComPanY<br />
s9-w46<br />
An Intelligent Solution to frontal and Side Impact Protection<br />
S. Murtuza<br />
iili;;tt-Y of Michigan-Dearborn<br />
sg-o47<br />
Ontimized Passenger Safety ln the Cbmpact Class<br />
Pttr. nt.-t"g' U' Seiffert<br />
Volkswagen aC<br />
Conlents<br />
1192<br />
1194<br />
1201<br />
' '<br />
1205<br />
1213<br />
1220<br />
1w<br />
1734<br />
1245
13th lnternatlonal Technlcal Conterence on Experimentel Sefety Vehtctes<br />
Technical Session 10: Heavy Truck Safety<br />
Chairperson: Bernd Friedel, Federal Republic of Germany<br />
s10-o-0L<br />
targe Truck Safety in the U-S. . 1,ZST<br />
Henry E. Seiff<br />
Motor Vehicle Manufacturers Association of the U.S., Inc.<br />
s10-o-02<br />
Typical Risk Situations in Car to Truck Accidents-<strong>The</strong> Necessity of Improving<br />
the Conspicuity of Trucks<br />
M. Danner, K. l,angwieder, H. B5umler<br />
HUK-Verband<br />
s1.0-o-03<br />
Improving HGV Safety-Front Undemrn Guards and Anti-Lock Braking Systems 7275<br />
B.J. Robinson, B.S. Riley<br />
Transport and Road Research Laboratory<br />
s1.0-o-04<br />
PassengerProtectioninSingleandDouble.DeckerCoachesinTippingover.<br />
P. Botto, M.C. Caillieret/ A. Patel, Institut de Recherches Orthopddiques<br />
C. Got, Institut de Recherches Biomdcanique et Accidentologique<br />
C. TarriEre, Renault<br />
sl0-o-05<br />
l?'ll"-fr-slH#:"''."#+:f,l.*l:l':::l.::1i::..T.:'*'"*Beh<br />
Andreas Schindler<br />
niv rureinland e.V.,Institute of Traffic Safety<br />
sl0-o-05<br />
Reliability, Maintalnabitity, and Dwability of Heavy Truck ABS Systems . . tzgl<br />
Robert M. Clarke<br />
National Highway Traffic Safety Administration<br />
s10-o-07<br />
NewConceptofBrakeforHeavyDutyVehicle.;...<br />
Tohru Kuwahara<br />
''l_<br />
i:If,Tffifi':<br />
Sumitomo Metal Industries Ltd.<br />
s10-o-08<br />
Experimental Accident Simulation for Improved Safety of Tank vehicles<br />
forDangerousGoods.... 1318<br />
K..Rompe<br />
TW Rheinland e.V.,Institute of Traffic Safetv<br />
s1.0-o-09<br />
UNITAS 2fiX}-Environment and Nature Protection Related Integrated Tanker Safety 1324<br />
Hans-Eggert Tonnesen<br />
Anton Ellinghaus GmbH & Co. KG
s6.o.0t<br />
Pivotal Characterization of<br />
A.C. Malliaris, J. H. DeBlois<br />
DeBlois Associates. Inc.<br />
Technical Session 6<br />
Light Vehicle Rollover<br />
Chairperson: William Lcasure, Unitcd States<br />
Car Rollovers<br />
Abstract<br />
This paper addresses and traces the influcncc of<br />
several rollover pre-initiation, independent, variablcs on<br />
intermediate and final outcomes, regarding the crashing<br />
car/occupant complex system and the resulting casualties.<br />
<strong>The</strong> primary vchicles under investigation are cars.<br />
<strong>The</strong> data for the development of the desirecl results arc<br />
extracted from the US ficld cxpcrience of rollover<br />
involvcd cars and car occupants. Six independent variablcs<br />
are addressed in the rollover pre-initiation stage:<br />
car travel speed, roadway speed limit, car malteuver,<br />
accident precursor, first harmful evcnt, and the location<br />
of this event. Five intermediate outcomes are distinguished:<br />
the number of quarter turns; loss of passenger<br />
compartment integrity through doors that come open<br />
in the crash; loss of integrity through disintegrated<br />
glazing; occupant ejections, complete or pflrtial; and<br />
intrusion of roof, roof borders, and pilhrs. <strong>The</strong> final<br />
outcomcs addresscd in the investigation are occupant<br />
fatalities, injured survivors, and overall harm. A most<br />
informative aspect of this investigrtion is the comparative<br />
evaluation of rollover versus nonrollover crashes.<br />
Car travel speed is found to be the source of profound<br />
differences. Ciu travel speed is suggestcd its a most<br />
informative descriptor of "rollover severity," especially<br />
when considered in conjunction with accident precursor<br />
and car mancuver conditions that promote lateral speed<br />
development.<br />
Introduction<br />
Because of the complexity in the relationship between<br />
circumstances and outcomes in rollover associated<br />
crashes, a rollover severity descriptor and pivotal<br />
determinants of outcomes have bccn elusive goals to<br />
date. This paper develops the foundation for achicving<br />
these goals.<br />
In addition to their demonstrable influence on rollover<br />
outcornes, the independent variables in this investigation<br />
are emphasized on the basis of two criteria: (a) availability<br />
in the rccords of accident experience: and (b)<br />
applicability in dynamic simulations and tests of rollovers.<br />
<strong>The</strong> purpose of this investigation is to establish<br />
the grounds flor useable parameters, and a range of<br />
pertinent values for these parilmeters, that influence<br />
profoundly car rollover outcomes, as obscrved in the<br />
accident expericnce, at all stages between pre-rollover<br />
maneuvers and final outcontes.<br />
Note that thc scope of the paper is limited to the<br />
investigation of rollover attributes as they influence the<br />
severity of this event and its outcrrmes, inespective of<br />
conditions that prolnole or reduce rollcrver propcnsily.<br />
Background<br />
Rollover is a serious highway threat. In the US, nearly<br />
10,000 people iue killed each year in crashcs of rollover<br />
involved motor vehicles: about 6.000 of these fatalities<br />
are occupflnts of cars.<br />
In spite of such conccrns, littlc progress has been<br />
made to date in sericlus itnd quantitnlive rcsearch of<br />
rollover. This is so not only because of the complexities<br />
of rollovcr associated crashes, but also because r-rf the<br />
frct thflt urttil rcccntly ncither the data nor the analyticitl<br />
tools wcre availablc [o conduct $uch research.<br />
In addition to a missing descriptor of rollover severity,<br />
and missing pivotal dctenttinants of rollover outcomes,<br />
also missing is a rollovcr tast protocol that rcpresents<br />
adequfltcly the unfolding of rollover events, postinitiation.<br />
All of these flre important prerequisites for the<br />
formulation of rollover perfortrtance requirements, and<br />
for the development and evaluation of proposcd intcrventions<br />
aimed at casualty reduction.<br />
Rollover crashes havc bccn usually chrracterizecl by a<br />
large number of paramctcrs, that may influence rollover<br />
outcomes at a varying itnd oftcn unknown dcgree.<br />
Examples of such pilrilrlleters arc thc tcrrain topography<br />
and the time of the rollover crash; thc first lr:rrnrful cvcnt<br />
and its location with respect to the roadway; roldway<br />
grade, curvature and surface conditions.<br />
Although such parameters provide good background<br />
for rollover research, they are marginally usc[ul in<br />
establirrhing the reliltively few, simple, and pivotal<br />
conditions needed in dyntmic simulation or tcsting of<br />
cars for crashworthiness pcrformrnce in rollovers.<br />
Two useful parilmeters suggested by lhis invcstigation<br />
are: a car's translational velocity (availablc through an<br />
estimate of thc car's travel speed or through the roadway<br />
speed limit) and the likclihood of an angulur impulsc,<br />
developing as a result of pre-rollover car stfltes that<br />
promote latcral slide, irresgtcctive of circurnslitnccs that<br />
lcd to such states.
ISth lntemetlonel Technlcel Conference on Experlmentel Setety Vehlcles<br />
Data Sources and Applications<br />
Bccause of lhc required many categories of variables<br />
and nccdcd resolution, the primary source of data used<br />
all across the board in this investigation is thc US<br />
National Highway Traffic Administration's (NHTSA's)<br />
National Accident Sampling System (NASS).<br />
Within this system, wc rcly primarily on the nationally<br />
representative sample of the NASS/crashworthiness Data<br />
System, [NASS/CDS 1988-19901, concerning cars of<br />
recent vintage and othcr light vehicles that were towed<br />
away due to crash damage in the US, in 1988-1990.<br />
<strong>The</strong> sample counts, i.e. the counts before inflation to<br />
national estimate levels, available within this system for<br />
the investigation of rollover injuries are: about 1,400<br />
rollover involvcd cars and 2,000 rollover exposed occupants.<br />
Most of the attributes of interest in this invcstigation<br />
arc available for these sample counts.<br />
Because of the relatively small samplc of fatalities in<br />
the NASS we address NHTSA's Fatal Accident Reporting<br />
System [FARS 1988-901, census of all ffltal<br />
accidents, every year on US roads, to obtain baseline<br />
fatality counts. This source of data providcs us with a<br />
rollover involved populations of about 16,400 cars and<br />
17,500 occupant fatalitics.<br />
In conjunction with the above, for general estimate<br />
purposcs, we address a companion file: the NASS/<br />
Gencral Estimates System which is a national sample of<br />
all police reported accidents in the us TNASS/GES<br />
1988-19901. <strong>The</strong> sample of rollover involved cars in this<br />
file is about 4.200.<br />
Furthermore in integrating all casualties, whether<br />
fatalities or injured $urvivors, we apply the "Harm"<br />
descriptor as a bottom line measure of all casualty<br />
outcomes. Several dala sources of injury outcomcs and<br />
injury costs have been reviewed for this purpose. Particularly<br />
applicable are the cost and injury outcome<br />
schedules appcaring in the work of Miller et al<br />
conducted in the Urban Institute, [Miller t99la], [Millcr<br />
l99lbl, and [Miller l99lc].<br />
Perspective<br />
Rollover Involved Cars and Car Occupants<br />
About 11,600,000 motor vehicles of all body types<br />
become crash involved every year on US roads. This is<br />
an annualizcd average for 1988-1990, according to<br />
NASS/GES. Of these, about 877o or 10,200,000 are light<br />
vehicles used for personal transportation including:<br />
8,200,000 cars, 1,300,000 pickups, 410,000 vans, and<br />
260,000 multipurpose vehicles (MPVs) pcr ycar.<br />
Only a small proportion of these crash involvement<br />
rates are rollover related. This proportion for cars is<br />
l.74Vo and represents about 142,000 cars per year. However<br />
the corresponding proportion for casualties and<br />
harm is much higher.<br />
For example, the fatalities associated with rollover<br />
exposed occupants represent more than 25% of all car<br />
occupant fatalities. This is $o because of the high<br />
722<br />
severity of the rollover crashes in general, an
and the three degrees of ejection (none, complete and<br />
partial) for car occupant$ exposed to rollover crashcs.<br />
Unrestraincd, Nonejectcd<br />
37.6Vo<br />
Unrestrained, Completely Ejected 37.1Vo<br />
Unrestrained, Partially Ejected<br />
8.6Vo<br />
Restrained, Nonejected<br />
14.3Vo<br />
Restrained, Completely Ejected<br />
0.4Vo<br />
Rcstrained, Partially Ejected<br />
t.4vo<br />
Total<br />
100.07o<br />
Based on the data sources used in this investigation,<br />
safety belt use by car occupants on US roads in 1988-<br />
1990 is estimated to be about 507o, varying very significantly<br />
as a function of crash mode, crash severity, and<br />
occupant demographic attributcs. In addition safcty belt<br />
use rates are often mischaracterized due to occupant<br />
reporting inaccuracies.<br />
Accordingly, the relatively small harm proportions<br />
cited above for rcstraincd occupants, should not be<br />
entirely assigned to safety belt effectiveness. Other<br />
factors that may account for the said small harm proportions<br />
are: (a) a much lower belt use rate in rollovers, e.g.<br />
under 207o; and (b) when exposed to rollovers, belt using<br />
car occupants are most likely involved in less severe<br />
rollovers than unbelted occupants, as a result of more<br />
safety awareness.<br />
Further IIarm Distributions.In order to conclude the<br />
general perspectivc addrcsscd in this section wc show<br />
further distributions of rollover exposed car occupants<br />
and of the harm they incur. This is done in Table 2<br />
bclow.<br />
Table 2. Hollover Erpoced car Occupants and<br />
Harm Distribution<br />
All<br />
Diatributeal bY!<br />
Tfavdl Sp66d, sph<br />
40 or Under<br />
41 to 60<br />
Over 60<br />
By CraEh TlFe<br />
Slngle v6hlcl6<br />
MuIti-vehlcle<br />
By Rollover Axis<br />
Ro11<br />
Pltch<br />
By Quart€r<br />
OnE<br />
TumB<br />
Two or Thre€<br />
Four or lldrd<br />
By Ejection OccurrencE<br />
No<br />
Yc3<br />
occupantr Hnil Rclrtlvc Hail<br />
Percent Percrnt per Occupant<br />
100. 0<br />
26. 0<br />
53.1<br />
20. 9<br />
87. 3<br />
L2,7<br />
96. 4<br />
3.6<br />
L7.Z<br />
{e.l<br />
33.7<br />
9r. 0<br />
9.O<br />
100.0<br />
11.0<br />
40.9<br />
48, r<br />
77.t<br />
22.7<br />
94.6<br />
5.4<br />
10. 1<br />
35,5<br />
54.4<br />
{4.3<br />
55.7<br />
l. 00<br />
o.42<br />
o,77<br />
2. 30<br />
o, 89<br />
L.79<br />
o. 98<br />
1, 50<br />
o. 59<br />
o,72<br />
1, 6t<br />
0, 49<br />
6. 19<br />
Note that Percent Occupants and Percent Harm in this<br />
Table add to 10070 in each part of the table. Also note<br />
Sectlon 3: Technleal $esslons<br />
that the Relative Harm per Occupant is the Percent Hrrm<br />
divided by thc Pcrccnt Occupants. As such it is alwirys<br />
equal to 1.00 for the total in cach part of Table 2.<br />
Three of the attributes shown in Table 2. Car Travel<br />
Speed, Numbcr of Quartcr Turns, and Ejcction Occurrence,<br />
are discussed extensivcly in latcr sections.<br />
However at this point consider two signil'icant rollover<br />
attributes: the Number of Vehicles involved in rollover<br />
events and the Primary Rotation Axis.<br />
Specifically, note that the large majority of car rollovers<br />
are single driver accidcnts, and that the rollover<br />
axis is almost exclusively the car's roll axis. <strong>The</strong><br />
proportion of end-over-end car rotation (pitch) is vcry<br />
small. In view of these circumstances, this investigation<br />
will focus primarily on roll axis rollovers, without<br />
reference to thc number of vehicles involved in the<br />
crash.<br />
Criteria in the Selection of Key Variables<br />
Thc invcstigation has provided substanlial perspective<br />
for car rollovers in relation to a number of characteristics,<br />
but most of the attributes discussed so far are not<br />
particulilly helpful in thc formuhtion of eilher rollover<br />
tcst or dynamic simulation protocols. Morcovcr no major<br />
suggestions havc bccn advanccd yet for thc sclcction of<br />
one or a few varirblcs to rcprcscnt<br />
"rollovcr<br />
scverity."<br />
Key variables for the invcstigatiorr will bc selcctcd in<br />
each of thc three rnain areas of intcrest: pre-crash,<br />
intermediate outcomes, and final outconles. For clarity,<br />
pre-crash variables arc bcst thought of as indcpcndent<br />
variables, while the intcrmcdiilte lnd finrl outcomes iuc<br />
the dependent variables.<br />
A preliminary list of key vrriables is limited first by<br />
the availability of such variables with appropriate resolution<br />
in thc accidcnt records. In addition, priority considerations<br />
for key varirbles in the prc-crrslr shgc are<br />
established on the bnsis of a variable's strength of<br />
influence on intermediate and especially final outcolnes.<br />
For the investigation reported here, pre-crash vitriablcs<br />
are prc-rollovcr variables addrcsscd fronr the vicwpoint<br />
of what happcns oncc rollovcr has trccn initiatcd, without<br />
any relevance to the question of whcther or how rollover<br />
is initiated.<br />
<strong>The</strong> most important criterion in the selection of such<br />
key variables is thcir applicability to bc uscd simply and<br />
readily ns pivotal pilrrlmeters in dynrmic simulittions or<br />
testinE of cars in the post-initiation stages of rollover,<br />
lcading to rcsults conccrning intermediate and final<br />
outcomes.<br />
For exarnple, a car's travel speed, preceding the rollover,<br />
is both influential and praclicflble. By contrflst,<br />
variables such as thc urban or rural location of the crash,<br />
or the location of the first harmful event (whether on the<br />
roadway or off it), rnay be inl'luential but iue neither<br />
simplc nor practicallle pivotal pararneters in rollover<br />
simulations or testins.<br />
723<br />
;t<br />
'q<br />
+<br />
F:<br />
4<br />
-i<br />
11<br />
j:i
13th lnternetlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
Key Pre-Rollover Variables<br />
In order to apply the criteria discussed above, we<br />
address the following pre-crash variables: Car Travel<br />
Speed, Roadway Speed Limit, Car Maneuvcr, Crash Precursor,<br />
First Harmful Event, and Location of First<br />
Harmful Event. <strong>The</strong>se are examined $eparately in crashcs<br />
with and without rollover occurrence, for comparison.<br />
Car travel speed, is a prime candidate for a piyotal<br />
parameter, because, as will be shown shortly, it has a<br />
very strong influence on both intcrmcdiate and final<br />
outcomes of rollovcr crashes, as well as it is praclicable<br />
for applications in rollovcr tcsts and dynamic simulations.<br />
Car travel speed is available both in thc NASS and in<br />
the FARS accident records, although in about 507a of the<br />
records. For this reason, the distribution of cach kcy<br />
variable in the investigation, whether dcpcndent or<br />
independent, was chcckcd for relative agreement and<br />
consistency, in a comparison of the two accidcnt rccord<br />
populations: one with known antl the other with unknown<br />
car travcl specds.<br />
<strong>The</strong> results of this comparison show no signiticant<br />
differences between the two populations and thus suggest<br />
that it is a fair approximation to usc thc records of<br />
known car travel speecls for the characLcrization of all<br />
records in the NASS and FARS uscd in this investigation.<br />
Furthcrmore, in order to sfiengthen the analyses based<br />
on estimated travel speed, we also address the readily<br />
available roadway speed limit, a lair surrogate of travel<br />
speed, as an additional independent variablg. <strong>The</strong> working<br />
assumption here is that car travel speed is at least as<br />
high as the roadway speed limit, especially at night when<br />
rollovers show a high incidencel and in roadways<br />
through non hcavily populated areas, where most of the<br />
rollovcrs take place.<br />
Car Maneuvcr (pre-crash) as a variable is offcrcd in<br />
both the NASS and the FARS data sources. This variable<br />
assumes several possible values conccrning car travel<br />
well before critical conditions developed, lcading<br />
ultimately to a crash. Examples of such maneuvers are:<br />
Going Straight, Negotiating a Curve, Passing, Lane<br />
Changing, Slowing in Traffic, Starting in Traffic, ctc.<br />
Crash Precursor is an independent variable otl'ered<br />
only in the NASS, whcrc it is known as the "Type of<br />
Accident." <strong>The</strong> valucs assumed by this variable are<br />
vehiclc specific and help identify what transpircd in the<br />
relatively short time, say scconds, before a crash<br />
occurrence became inevitablc.<br />
Examples of values assumcd by the Crash Precursor<br />
are: many distinct configurations in lwo vehicle crashes<br />
such as vehicle path crossings, head on paths, head to<br />
rear paths, and sideswipes; and many single driver crash<br />
configurations. Of particular intcrcst in a rollover<br />
invcstigation are values such as: roadway departure,<br />
collision avoidance, loss of control, or loss of traction.<br />
't24<br />
Two more variables are addressed as independent variables:<br />
the First Harmful Event (FHE), ilnd lhc Location<br />
of FHE relative to thc roadway. Both variables are<br />
available in both the NASS and FARS.<br />
Beyond thc six independent variables mentioned<br />
above, an examination of all othcr avlriltltlc variablcs<br />
rcvealed only weak candidates for pivotal independcnt<br />
variables.<br />
<strong>The</strong> Importance of Travel Speed<br />
<strong>The</strong> proportion of cars trirveling rt {l given speed is<br />
shown in Figure l, as a function of this speed, for ull<br />
police reported car crashcs, rollover involved and all<br />
other.<br />
FroForilcn of Sxtr, Fcrcant<br />
F. - - i:..-j-_::::-.<br />
_ I ;<br />
OL<br />
Undar 20 20-30 3o-4o 40-60 50-60 Over 60<br />
Car Travel Speed, mph<br />
+ Rollov€r<br />
-+- No Follffit<br />
"ililffiff;:t"td in crashes ot Atl severities<br />
A major difference between thc shown distributions is<br />
evident, sincc the distribution for rollovers is clcarly<br />
shiftcd by morc than 20 mph towud higher trlvel<br />
speeds. <strong>The</strong> mcan speeds l'or these distributions are: -50.1<br />
mph for the rollover involved cars, and 27.7 mph for<br />
cars in all other crashcs.<br />
Another illustralion of travel speed distributions is<br />
shown in Figure 2, for cars involvcd in latal accidcnts.<br />
<strong>The</strong> same major dittcrcncc bctwecn rollover and non<br />
rollovcr distributions is evidettt. In this case the mean<br />
speeds are: 63.4 mph for the rollovcr involvcd cars, and<br />
45.3 mph for cars in all other crilshes.<br />
'io<br />
Proportiofi ol Cert, Perdent<br />
und6r 20<br />
5ouE.r ?h. FAi6 fiat.lsgo<br />
20-30 30-40 40-50 50-60<br />
Car Travel Speed, mph<br />
+ Rollover<br />
-+- No Rollov€r<br />
Figure 2. Car Travel Speed In Fatal Crashes<br />
Over 60
<strong>The</strong> large proportion of travel speeds above say 50<br />
mph, for rollover involved citrs, and the large disparity<br />
between rollover and non rollover travel speed distributions,<br />
is not limited only to thc data shown in Figures I<br />
and 2. As shown in Table 3, high travcl spceds of rollover<br />
involved cars, and the rollover/nonrollovcr disparities<br />
are evident in every available source of data, concerning<br />
cars, occupants, occupant fatalities, and harm in<br />
general.<br />
Tabh 3. Distribution of Car Rollovsr Hecords<br />
over Cer Travel Speeds, 1988-1990<br />
(1) Carr in AII Pollcd Rdpdftod Rollov.ra [t{A,SS/cEs]<br />
(2) TourHay Rqllover Involv.d ctrra [HNs/CDs]<br />
(3) Rollovor Involved Care in FdtBI Accldgnts [FM]<br />
(4) Rollover Expoe.d occupant€ ln TocnHAy cars INASS/CDs]<br />
(5) FatalltieB ln Car Rollovers [FNs]<br />
(5) fotal Ham (Fatalltl€E & surivors) in Car Rellovers<br />
Rollovrr Accldsnt RgcordE<br />
Trlvrl<br />
Ep..d, nph t (3) r (4)<br />
t (5)<br />
20 E Undor 3,2 3.2<br />
31.-30 5. 1 e,3<br />
31-40 I7,3 t1.1<br />
41-50 25.9 24.7<br />
5l-60 28.2 28. 3<br />
Over 60 19. I 20.1<br />
r.6 3.{<br />
1.3 5.8<br />
4.s 16.7<br />
1t.0 25.8<br />
2A.O 27,2<br />
52.4 2O.8<br />
Totrl 100. o 100.0 100.0 100. o<br />
EGan (bph)<br />
for R/o 5O.0 5r,2 63.4 50.3<br />
il.an (nph)<br />
for AII Oth.r 27,7 31.9 a5.3 e8.1<br />
1.6 1.1<br />
t.e 1.9<br />
{.1 8.0<br />
tt.5 r4,7<br />
54.0 48.0<br />
loo.0 100,0<br />
6'1.5 5o.5<br />
{6.5 38.5<br />
Furthermore, the cited findings are confirmed by a<br />
dctailed analysis of thc readily available roadway spccd<br />
limit, a fair surrogatc o[ travel speed.<br />
An illustration of results concerning the distribution of<br />
cars, either rollover involved or involved in othcr crashes,<br />
over the roadway speed limits is given in Figurc 3. A<br />
summary of similar results from sevcrirl other sources is<br />
presented in Table 4.<br />
Proportion of CarE, P6rc6nt<br />
BO-<br />
50<br />
Und6r gO 30 to 40 46 to 50 55 & Over<br />
Foadway Speed Limit, mph<br />
gouro} Th. HAgg/COg rgEa-t99o<br />
. I Rottovor N Ho Roilovcr<br />
Figure 3. Proportione of Hollover Involved End Other<br />
Cresh Involved Cars e$ Function of Roadway Speed Limit<br />
It is evidcnt that these results are essentially consistent<br />
with the conclusions reached earlier conccrrring the lilge<br />
proportions of rollovcr involved cars that travcl at high<br />
speeds, say above 50 mph.<br />
Sectlon 3: Technlca/ Sessions<br />
Tsble +. Dlstrlbutlon of Car Hollover Hecords<br />
ovsr Hoadway<br />
Speed Limits<br />
Roadway<br />
Sprid<br />
LiDit, Dph<br />
(Each CoIuEn Addc ItF to 100t)<br />
(r) crrr In All Police R6ported Rollov€rE tNAss/dEsl<br />
(2) TtraHay Follovar Jnvolvad caEs [NAss/cDs]<br />
(3) RoIIov.r rnvolv6d carr ln Fatal Accidents IFARS]<br />
(4) Rollover ExpoBdd occupentB ln Towaeay carr ItlA86/CD8]<br />
(5) Fatalitiss in car RoIIovBra LFARSI<br />
(6) Total IIaru (FatalltleE fr surulvora) in cer RoIIovarE<br />
und6r 30 5.{<br />
30 to 40 I9.7<br />
{5 to 50 r9.{<br />
55 & Cvir s5.5<br />
Rollaver Aqqident RecordB<br />
t {r) t (2) r (3) r (4) t (s) + (6)<br />
4,3 2.9 7 ,2<br />
t6.4 1{.4 20.7<br />
tg,t 12,9 20,3<br />
{9.F 68,0 51,9<br />
2.9 3.9<br />
14.4 13 .8<br />
69.6 60. {<br />
As recalled, the working assurnption in rcllting roadway<br />
speed limit to car travcl speed is thal car travel<br />
spccd is at least as high as thc roadwity speed limit,<br />
espccially at night when rollovcrs slrow a high incidence:<br />
and in roadways through non-heavily popuhted areas,<br />
where most of thc rollovers take placc.<br />
Potential for Lateral Slide<br />
Lateral car slidc is a condition likely to promote roll-<br />
over. Howcver. the availablc car accidcnt rccords olfer<br />
no measures of lstcral velocity. For this rcason wc luke<br />
advantage of the rcsolution offered in the rccords of Crr<br />
Maneuvcr and/or Crash Precursor, discussctJ carlicr, in<br />
orrJer lo producc a cornposite vlriable lhat we shall cirll:<br />
"Laleral<br />
SIidc Polcntiirl" thrt is potential l'or latcral<br />
veloc ity devclogrrncnt.<br />
Our intcrest in addrcssing the varirbles: Car Maneuver<br />
and Crash Prccursor in this investigatiolr is cvidcrrt from<br />
the point o[ vicw of conditions, in cithcr orlc or in both<br />
variablcs, that lcad to lirteral velocity dcvclopmcnl.<br />
An illustration of the distribution of car mancuvcrs<br />
encountered in fatill car accidents is given in Figurc 4,<br />
concerning rollovcr involverJ cars as well as cars involved<br />
in othcr crashcs. It is evident in tlris figure that<br />
rollover has r higher incidcncc l'or rn{lncuvers such as<br />
"Ncgotiating<br />
Curve,"<br />
"Avoidtncc," "Lane<br />
and Change"<br />
maneuvcrs such us passing, nrcrging. clc.<br />
Car Maneuver<br />
Going Stralght<br />
Ncgotiaiing Curw<br />
AvoidancE Man6uv6t<br />
Par|lng, Mrrging<br />
Slow Mancuver<br />
Turn ing<br />
Souro.: Thr F hC lftt-leeo<br />
O 20 {40 BO<br />
. ?roportlon of Cars, Percent<br />
@ Rotlovar N No Rottowr<br />
Figure 4. Car Maneuver Proportion$ in Rollover and<br />
Non-Rollover Crashes<br />
725
lSth lnternatlonal Technlcal Gonterence on Expertmentel Sefety Vehlctes<br />
<strong>The</strong> Crash Precursor, is an event that may be concurrent<br />
with or follow a maneuver. A relevant grouping<br />
and distribution of Crash Prccursor valucs for rollovcr or<br />
nonrollovcr crashes is shown in Figure 5. <strong>The</strong> predominant<br />
proportions of certain maneuvers for rollover<br />
involved cars is evident, including "Loss of Control,"<br />
"Roadway<br />
Departure" and<br />
"Avoidance."<br />
Precuraor<br />
LoEE of Control<br />
Drivr Oll Thr Roed<br />
AvOidance Mancuy6r<br />
All Other<br />
Bqurcr' Thr NAES/6EB re{8.rte0<br />
20 40 60 80 100<br />
Proportion ol CErr, Percent<br />
@ Rotlover Nl No Fottovg<br />
Figure 5. Crash Precursor Proportions in Rollover and<br />
Non-Hollover Crashes<br />
With full awareness that variables: Car Maneuver and<br />
Crash Precursor, have limitations, wc formulatc a composite<br />
variable assumcs paircd values as shown below:<br />
. No, No: (No Negotiating Curve, No Lane Change;<br />
No Collision Avoidance); (No Roadway<br />
Departure; No Loss of Control; No Loss of Traction)<br />
. Yes, No: (Negotiating Curve, or Lanc Changc, or<br />
Collision Avoidance); -- (No Roadway Dcparturc;<br />
No Loss of Control; No Loss of Traction)<br />
. No, Yes: (No Negotiating Curve, No Lane Changc;<br />
No Collision Avoidance); -- (Roadway Departure or<br />
Loss of Control or Loss of Traction)<br />
. Yes, Yes: (Ncgotiating Curvc, or Lane Change or<br />
Collision Avoidance); -- (Roadway Departure or<br />
Loss of Control or Los$ of Traction)<br />
where the first parcnthcsis in each case designates values<br />
assumed by thc Car Maneuver variable, while the second<br />
parenthesis refers to values assumcd by thc Crash Prccursor<br />
variable.<br />
In a further simplification we define the lateral slide<br />
potential to be low under the'-No, No" conditions , and<br />
"Yes,<br />
high under conditions: No,"<br />
"No,<br />
or Yc$"<br />
"Yc.r,<br />
Or<br />
Yes."<br />
Intuitively speaking, we would expect a small likelihood<br />
of rollover when the lateral slide potcntial is low,<br />
while a high potential for lateral slide would lead us to<br />
expcct a high lik0lihood lor rollover.<br />
<strong>The</strong> accident experience validates this notion. Specifically,<br />
we find that the lateral slide potential is high in<br />
83.ZVo of the rollovers (versus in 27.3Vo of other crashes),<br />
while the lateral slide potential is low in 16.87o of<br />
the rollovers (versus 72.7o/o of other crashes).<br />
Intermediate Outcomes<br />
Intermediate outcomes is a collective characterization<br />
of depcndent variablcs that follow thc indcpendent variables<br />
in the chain of events thal unfold in a crash. Five<br />
intermediatc outcomcs lrc distinguished in this investigrtion,<br />
bascd on availnhility in thc accidcnt rccords and on<br />
desired resolution.<br />
Thc five intermediate outcomes are: (l) the number of<br />
quarter turns in the rollover; (2) loss of plssenger<br />
compartment intcgrity through doors that comc opcn in<br />
the crash; (3) loss of integrity through disintegrated<br />
glazing; (4) occupant ejections, complete or partial; and<br />
(5) intrusion of roof, roof bordcrs, and pillars.<br />
Wc now address cach of thcsc intcrmcdiatc outcomcs<br />
as a function of the most importilnt pre-crash variable,<br />
namely car travel spccd.<br />
Number of Rollover Quarter'I'urns<br />
<strong>The</strong> number of qulrrter turns (QT) is an impurtant<br />
intermediate variable. lt is al$o a strong link between<br />
pre- and post-rollover initiation conditions. Moreover, it<br />
may be a good candidatc for "rollovcr<br />
scverity," in addition<br />
to or insteird of thc prc-rollover car speed, irs will be<br />
seen later in this investigation.<br />
Based on available resolution, QT in car rollovers<br />
assumes the values: one, two or three. and four or ntore.<br />
Rollover involved curs, irrespectivc ol' lruvcl spccd, iue<br />
distrihutcd as follows:<br />
17.1Va with QT = l,<br />
39.1%t with QT = 2 or 3, and<br />
43.2Vo with QT = 4 or tttore<br />
100.07o Total<br />
However, this mix is very sensitive to a car's travel<br />
speed as seen in Table -5 below.<br />
Teble 5. Car Hollover Quarter Turns ae a Function of<br />
Car Travel Speed<br />
Ros ProFortlon, * by<br />
Car Travel<br />
Car Rollover Quarter TufirE<br />
Speed, nph 2or3 4 or More<br />
40 or Le6E<br />
41 to 50<br />
51 to 60<br />
Qver 60<br />
3?.3 39. e<br />
19. 0 48,9<br />
7,Q 42.4<br />
7 .2 19.6<br />
22.6<br />
32,0<br />
50.5<br />
73.2<br />
total<br />
Percent<br />
100.0<br />
100.0<br />
100.0<br />
100.0<br />
Esscntially, thc proportion of cars wirh 4 or more<br />
quarter turns increases steadily as the travel speed<br />
increascs, whilc thc proportion oI cars with a lowcr QT<br />
is stcadily rcduccd.<br />
This is an indication that rollover severity increases as<br />
car travel speed increases, given that an increasing<br />
number of QT introduccs highcr risks of (a) loss of<br />
pilsscnger compilrtment intcgrity; (b) occupirnt ejections;<br />
(c) roof and roof support intrusion: and (d) harmtul<br />
occupant contilcts.
Loss of Pawen&er Compartment Integrity<br />
(Through Doors)<br />
<strong>The</strong> proportion of rollover involved cars with a door<br />
that comes open during the rollover is about 8%,<br />
averaged over all car travel speeds or eTs. This<br />
proportion shows the following sensitivities:<br />
. Car Travel Speed, mph:<br />
40 or Less<br />
t.0%<br />
4l to 50<br />
2.9Vo<br />
5l to 60<br />
4.SVo<br />
Over 60<br />
28.rVo<br />
. Number of Quarter Turns:<br />
I<br />
3.7<br />
2to3<br />
5.2<br />
4 or More<br />
13.8<br />
Loss of Passenter Compartment Integrity<br />
(Through Glazing)<br />
<strong>The</strong> proportion of rollover involved cars with at lea$t<br />
one window (including windshield and roof window)<br />
entirely disintegrated is about 657o when avcraged over<br />
all car travcl speeds or all QT's.<br />
In spite of such a large proportion for the average<br />
rollover involved car, there are still sensitivities<br />
as<br />
shown below:<br />
. Car Travel Speed, mph<br />
40 or Less<br />
4l to 50<br />
5l to 60<br />
Over 60<br />
. Number of Quarter Turns<br />
I<br />
2to3<br />
4 or More<br />
Car Occupant EJections<br />
Table 6 summarizes the car occupant proportions that<br />
are ejected in rollovers and, separately for comparison,<br />
in all other crashes. <strong>The</strong> same table also shows the harm<br />
to ejectees as a proportion of the harm to all rollover<br />
exposed occupant$.<br />
Tablc 6. Elected Gar Occupantc and Retaled Harm<br />
Deoree ol Electlon Hollover Craehes<br />
Complet6<br />
Pirtial<br />
Total Ej€ctionr<br />
t Ejeotit!<br />
40.7<br />
85. I<br />
67.2<br />
84.0<br />
35.0<br />
62.1<br />
87.7<br />
All Other CreEheg<br />
* EI.clr.r<br />
Compl.tc 6.99 o,ag<br />
Psrtlal z.gg O.gz<br />
Tot6l Eioctionr 8.S,t O.Bl<br />
I Harm t Her]F<br />
36.9 5,72<br />
10.8 6.84<br />
66.7 1e,36<br />
<strong>The</strong> proportions shown in Table 6 are averaged over<br />
all car travel speeds or over all QT values. <strong>The</strong>re is<br />
however a large variation in the proportion of ejectees<br />
Sectlon 3: Technfcal<br />
$esslons<br />
and of the ejection harm across the values assumed by<br />
car lravel specds or QTs in this invcstigation.<br />
For example, the value 55.7% appearing at the bottom<br />
of the Rollover column in Table 6, varics betwecn l07a<br />
and 78Vo as the car speed is varied from under 40 mph<br />
to over 60 mph. Similarly wide excursions are observed<br />
in ejection proportions as a functiorr of QT.<br />
Final Outcomes<br />
Fatalities, injured survivors, and lhe integration of<br />
these into harm have been addressed in several sections<br />
of this investigation, especially in the parr dealing with<br />
rollover exposed cflr occupants in perspcctive. We shall<br />
summarize hcre the principal findings.<br />
Based on data presented in earlier sections, thc rollover<br />
involvemcnt of car occupilnts is about I.75 per 100<br />
crash exposed; but the harm to rollover exposed occupants<br />
is about 2l7o of the harm to all crash exposed.<br />
This is a disparity of 12 to I and undcrscores thc need<br />
for casualty control in rollovers.<br />
Furthermore, harm distribution in rollovers, is vcry<br />
sensitive to car travel spced and, by association to the<br />
numbcr of rollovcr quartcr turns, and to ejection occurrence.<br />
This was discusscd in conncction with Table Z. As<br />
may be seen in this table wide variations tirke place in<br />
the harm per occupant, as the car travel speed varics<br />
from under 40 mph to over 60 mph.<br />
Similarly, a significant scnsitivity is seen in harm per<br />
occupant, as a function of thc number of quitrter turns in<br />
the rollover, and cspecially as a funclion of ejcctiorr<br />
occurrcnce.<strong>The</strong>sc sensitivities hold tor injured survivors<br />
as well as for fatalities.<br />
Conclusions<br />
In search of a pivotal charactcrization of cnr rollovers,<br />
this investigation addressed paramctcrs and values of<br />
paramctcrs that must be takcn into account in devetoping<br />
rollover simulation, and test and evaluation protocols,<br />
that are relatively simplc, practicablc, and rcprcscntative<br />
of conditions in the field experiencc.<br />
In addressing prc-rollover conditions, two parameters<br />
proved to be influentiirl: the c{lr travel speed, and the<br />
potential for lateral slidc development. Travcl speed in<br />
conjunction with thc lateral slidc potential appear to<br />
influence profoundly not only thc incidencc. but also the<br />
severity of rolklvcrs. <strong>The</strong>se parameters dcserve furthcr<br />
attention in the dcvcloprnent of a "rollovcr severity"<br />
descriptor.<br />
Travel speed is also the most important parameter that<br />
distinguishes rollovcrs from all other catcgories o[<br />
crashes. Rollover involved cars travel at a mean speed of<br />
50 mph (63.4 mph for fatal crashcs); by contrast cars in<br />
all other crashes travel ar 27.7 mph (45.3 rnph in fatal<br />
crashes).<br />
Inespective of this comparative evaluation, rollover<br />
test and dynamic simulation protocols will have to<br />
727<br />
1:<br />
j<br />
;<br />
f,<br />
'it
lgth tntemettonat Teahnl1et Conterence on Experlmentel Safety Vehlcles<br />
address these rather high speeds. This could be accomplished<br />
by either considering a pertinently high tcst or<br />
simulation speed in the travel direction or, if not, by<br />
introducing part of the energy thflt i8 implied by a highcr<br />
travel speed in a subsequcnt stage, e.8' as roll energy<br />
through an angular impulse.<br />
Acknowledgement<br />
This work is sponsored by the Division of Injury<br />
Control, Centers for Disease Control, US Department of<br />
Health antl Human Services, undcr a grant: -'<strong>The</strong><br />
Mechanics and Biomechanics of Rollover Casualtics"'<br />
This paper is a companion paper to: Digges, K" -'A<br />
Framework for thc Study of Rollover Crashworthine$s,"<br />
l3th Safety Vehicle Conference, Paris, France, November<br />
1991 (Paper No. 9l-56-0-05).<br />
References<br />
Digges, K., '*Recent<br />
Improvements in Occupant Crash<br />
simulation capabilities of the cvS/ATB Model," sAE<br />
880655, 1988.<br />
Digges, K., Malliaris, A.C., and Ommaya, A.' "<strong>The</strong><br />
Mechanics and Biomechanics of Rollover Casualties,"<br />
Wayne State Biomechanics Symposium, March 1991.<br />
Digges, K., "Application of Human Modcls to Evaluate<br />
lmprovements in Motor Vehicle Crash Safcty," 8th<br />
s6-o-05<br />
Analysis of the Factors Which Influence<br />
K. Digges, S. Klisch<br />
University of Virginia<br />
Introduction<br />
<strong>The</strong> research reported in this paper is a continuation<br />
of that reported by Cohen, Digges, and Nichols [1] and<br />
by Malliaris and DeBlois [2]. <strong>The</strong>se related papers report<br />
analyses of rollovcr crash data, and are publishcd in the<br />
lZth and 13th ESV Conference hoceedings. This earlier<br />
research proposed crash variables which were shtlwn to<br />
by data analysis to be indicators of occupant injury<br />
severity. <strong>The</strong>se "crash sevcrity" variables are needed to<br />
assist in defining test conditions for rollover evaluations<br />
and for setting goals for injury mitigation measures. <strong>The</strong><br />
objective of thc research rcported herc is to apply com'<br />
putcr modeling, supplemented by studies of "hard copy"<br />
documentation of rollover accidents and crash tests, to<br />
assess the influence of the crirsh severity indicators<br />
suggested in the literature.<br />
Past Research<br />
A summary of the data analysis research which<br />
describes the characteristics of rollover crashes in the<br />
United States is given in the earlier paper by Cohen,<br />
Digges, and Nichols, and will not be rcpeated here.<br />
728<br />
Conference of Mitthcmatical Modeling, College Park,<br />
Maryland, May 1991.<br />
Digges, K., Malliaris, A.C., Ommaya, A., and Mclean'<br />
"Characterization<br />
of Rollover Casualtics," 199 I<br />
IRCOBI, Berlin, Germany, Septctnber 1991.<br />
Digges, K., "A Framework for the Study of Rollover<br />
Crashworthiness," l3th Safety Vchicle Conference'<br />
Paris, France, Novembcr 199 l.<br />
"Fatal<br />
Accident Reporting System," Autonatcd Files,<br />
National Highway Traftic Safety Administration,<br />
Annual Issues 1988- 1990.<br />
Malliaris, A. C. and K. H. Digges, "Crash Protection<br />
Offered by Safety Belts," Proceedings of the llth<br />
<strong>International</strong> Conference on Safety Vehicles, Washington,<br />
DC, May 1987.<br />
Miller, T., et al, "<strong>The</strong> Costs of Highway Crashes," <strong>The</strong><br />
Urban Institute, Washington, DC, 1991.<br />
Miller, T., "<strong>The</strong> Comprehensive Cost of Motor Vehicle<br />
Injuries by Body Region and AIS Severity,"<br />
35th Annual Proceedings of the AAAM, 1991.<br />
"Ncw<br />
Miller. T.. and Associates Estimatcs of Highway<br />
Crash Costs," Thc Urban Institute Press, Washington<br />
DC, 1991.<br />
"<strong>The</strong><br />
National Accident Sampling System /CDS,'<br />
(NASS) Automated Files 1988-1990, National Highway<br />
Traffic Safety Administration'<br />
Rollover Crash Severity<br />
<strong>The</strong>sc earlier studies included the following observa'<br />
tions:<br />
. Ejections are cxtremely harmful cvents, and are the<br />
predominate causc of harm in rollovcr crashes.<br />
. In falal cra.shes, fatality odds for cjcctees are 6 to I<br />
times higher thalt for occupants not cjccted.<br />
. Injury and ejcction are related to number of quarter<br />
turns and distance traveled.<br />
. Extent of vehicle damage is related to injury<br />
sevcrity.<br />
' In most rollovcr crashes, the vehiclc has a signifi'<br />
cant latcral velocity component prior to the occur'<br />
rence of rollover.<br />
Papers dealing two different types of full scale car<br />
rollover tcsts havc been reportecl by Habberstad, et.al.<br />
[3] and Orlowski, et. al. [4]. Thc Orlowski paper documented<br />
pure roll tcsts of Chevrolets with and without<br />
roof reinforccment. Thc authors concluded that a roll<br />
cage did not reduce injury measures on a test dummy for<br />
thc vehicle and roll condition testcd. <strong>The</strong> Habbcrstad<br />
paper reported full vchicle testing which involved sevcrc<br />
tripping prior to thc roll. <strong>The</strong> tcsts showed that severe<br />
dummy impacts with the vehiclc interior could be<br />
induccd early in the rollover event.
Rohertson [5,6] found that fatal rollover of utility<br />
vehicles pcr 100,000 registered vehicles relative to cars<br />
during 1982-87 was strongly conelated to the sratic<br />
stability of the vehiclcs. Brewer and Harwin I7l<br />
examined vehicle, driver and environmental factors<br />
which could be deduced from Cardfilc and found that<br />
vehicle stability fflctor had a strong influence on rollover<br />
involvement risk.<br />
Malliaris [8] examined FARS and Cardfile to determine<br />
the significance of motor vehicle characteristics on<br />
rollover propensity, after controlling for nonvehicular<br />
influences. He found that wheelbase and stability factor<br />
were both influential. Four whecl drive vehiclcs also<br />
exhibited highcr rollover risks, after controlling for<br />
exposure differences.<br />
Mengert, et. al. [9] examined the single vehicle rollover<br />
risks for 40 vchicle make/modcls in the statcs of<br />
Maryland, Texas, and Washington. Vehicle stability<br />
factor and urban/rural location were found to be important<br />
predictors of rollovcr risk. Harwin and Emory<br />
[0J examincd the CARS data for precrash conditions.<br />
<strong>The</strong>y found that 80 to 90Vo of the rollovers wcre tripped,<br />
gcnerally by soil. <strong>The</strong>y reportcd that injury severity<br />
corrclated strongly with speed. Stability factor, and<br />
number of quartcr turns were also influential.<br />
Malliars and DeBlois [2] invesrigared 1988-90 NASS<br />
and found that vehicle pre-crash speed is a pivotal crash<br />
sevcrity parameter. <strong>The</strong> pre-crash speed for rollovcrs is<br />
much highcr than for other crashes. Approximately 50Zo<br />
of rollovers occur at speeds above 50 mph, compared<br />
with l07o for other crashes.<br />
Framework for the Study of Rollover<br />
Outcomes<br />
In studying the rollover phenomena, we are examining<br />
separatcly each of thc individual evcnts which influence<br />
the motion of the vehicle and its occupants. Our<br />
approach is to apply computcr models which have been<br />
devcloped and validated by NHTSA. <strong>The</strong>sc models<br />
includc the STI vehicle model for tripped rollovcr, the<br />
ATB Vchicle Model for vehicle post trip morion, and the<br />
ATB Occupant Model for occupirnt motion.<br />
<strong>The</strong> first event considcred is rhe tripping mechanism.<br />
<strong>The</strong> consequences to bc determined in this case are the<br />
pre-roll dynamics and kinematics of the vehicle, and<br />
those of each occupant. <strong>The</strong> STI Vehicle Modcl, and the<br />
ATB Occupant Modcl provide the instruments for this<br />
study. We apply these instruments to determine thc<br />
consequence of tripping for a matrix of initial conditions<br />
which represent thc rollover spcctrum in the field<br />
expcricnce. <strong>The</strong> result is a spectrum ofoutput conditions<br />
which arc used as input to study the next cvent.<br />
<strong>The</strong> second event considered is the frce roll and<br />
translation of the vehicle and its occupants attcr tripping<br />
and prior to the vehicle impacting the ground. <strong>The</strong> ATB<br />
Vehicle Modcl is used to predict vehicle motion and the<br />
Sectlon 3: Technlcal Sesstons<br />
ATB Occupant Model is used for occupants. This phase<br />
of simulation includcs the nrotion from the time thc lircs<br />
have lost contact with the ground until the first vehicle<br />
body-to-ground impact 0ccurs.<br />
<strong>The</strong> third event considcrcd is the first vehicle body-toground<br />
impact. This phase includcs the morion from rhe<br />
time thc vehicle roof or side irnpacts the ground, until<br />
the next impact. <strong>The</strong> consequences to be determined are<br />
the dynamics of the vchiclc and its individual occupants.<br />
Again, the ATB modcls rleveloped and validated by<br />
NHTSA are the instruments for this study.<br />
In a similar way, studies of fourth and fifth events can<br />
be constructed for those rollovers which involve multiple<br />
ground contacts. Consequently, a complete roll of scvcral<br />
revolutions can be simulated.<br />
For the purpose of our initial study, we are conducting<br />
paramctric studies lo cvaluate how crrsh variables influence<br />
thc first three events.<br />
Tripping Simulations<br />
<strong>The</strong> STI Tripped Rollovcr Model is used to simutare<br />
the tripping cvcnt. This model is descrihcd in References<br />
ll and 12.<br />
Thc STI model was dcveloped for NHTSA by Sysrcms<br />
Technology, Inc. This modcl is a sevcn degree of<br />
freedonr vehicle modcl which was developed to permit<br />
the analysis of conditions which producc tripped<br />
rollover. <strong>The</strong> nrodcl sinrulates a skidding vehiclc impact<br />
with a curb. <strong>The</strong> curb to wheel lorcc is characterized by<br />
four functions: (l) a spring force betwecn 0 lnd 2 inches<br />
of 2000 lb/in, (3) a constflnr wheel dcflcction force of<br />
4000 lb/in bctween 2 and 8 inches, (3) a spring forcc of<br />
8000 lb/in above 8 inchcs, and (4) a curb drmping forcc<br />
of.25 lb-scc/ft.<br />
<strong>The</strong> modcl permits the variation of vehicle geometry,<br />
incrtia, suspension, and external force parametcrs; and<br />
the magnitudc and direcrion of the inirial displacement,<br />
speed and acceleration.<br />
<strong>The</strong> model predicts the incidence of a dynamic instability<br />
which irrcversibly leads to rollover. Thc roll<br />
angle, roll rilte and roll acceleriltion flre all calculated at<br />
each tirne increment as lhc simulation progrcsses, and<br />
are available us output varithles. <strong>The</strong> simulation termi,<br />
nates whcn rollover is predicted.<br />
An initial application of rhe STI model was the evaluation<br />
o[ paramctcrs which are scnsilive to changcs in the<br />
tripping velocity. For this study, thc geometric and<br />
inertia properties were avcrages taken from the 38<br />
pa$ricnger cars publishcd in refercncc 13. Suspension<br />
properties were scalcd from the basclinc dlta providcd<br />
with the STI modcl. <strong>The</strong> tripping nrcchanism was a 6<br />
inch curb which rleveloped forcc properties as dcscribed<br />
earlier.<br />
<strong>The</strong> STI model prcdicts a large sensitivity of roll rate<br />
to lateral vclocity. <strong>The</strong> sensitivity is relatively indcpendent<br />
of car size, as shown in Fisure l.<br />
729<br />
{<br />
:<br />
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lSth lnternAtlonel TechnlCal Conlerence on ExPeflmental Safety Vehlcles<br />
FOLL FATE. BEV/SEC<br />
i--=- tion of the ellipsoids is discussed in reference 14. <strong>The</strong><br />
5<br />
output of the ATB simulation includes the time history<br />
/t<br />
of all lorces acting on the vehiclc, and the rcsulting<br />
g<br />
2<br />
I<br />
o<br />
eo<br />
_ SIIALL CAN<br />
30<br />
T.ATER^L VELOCITY. MPH<br />
- M|PSIZE ' LANOE CAF<br />
Flgure 1. STI ltlodsFTrlpping Veloclty Influence on Roll<br />
Rate (Three Car Sizet)<br />
A turther analysis of the factors which influence roll<br />
rate is prescnted in Figurc 2. This figure shows the<br />
sensitivity of roll rate to other variablcs which are<br />
independcntly increascd by 20Vo, <strong>The</strong> baseline case lor<br />
this analysis was a 20 mph tripped rollover. As anticipated,<br />
the latcral velocity has a large amplification factor<br />
on roll rate.<br />
PEFCEHT O{AHBE IH ROLL FATE<br />
r00<br />
EO<br />
LATEH^L YEL gF TIASS FOLL IHERT. TRACX WIDTH<br />
VARIABLE<br />
Flgure 2. STI iiodel - Roll Rate Change lor 20o/c Increase<br />
in Other Varlables 1zo-mph, .75 rev/eec Baseline)<br />
Vehicle dimensional and inertia parameters have varying<br />
influence on roll rate. As the car sizc increases, the<br />
mass, roll inertia, and track width all increase' <strong>The</strong><br />
offsetting influence on roll ratc among thcse paramctcrs<br />
reduce$ the sensitivity of roll rate to car size.<br />
Occupant motion during the tripping event is being<br />
simulated by the ATB Occupant model. This research<br />
will be addressed later, in the Discussion scction.<br />
Roll Simulations<br />
<strong>The</strong> dynamic conditions resulting from tripping, as<br />
predicted by the STI model can now be uscd as input<br />
data to the ATB vehicle and occupant models which<br />
have been validated for prcdicting thc post tripping<br />
motion of the vehicle and occupants. Thc ATB modcl<br />
has been used extensively by NHTSA and the Air Force<br />
to simulate vehiclc and occupant motion during a crash'<br />
<strong>The</strong> ATB Vehicle Modcl was developcd and validated<br />
by the Air Force Armstrong Aerospace Medical Laboratory<br />
(AAMRL). In this model, the vehicle is simulated<br />
by one inertia ellipsoid, and eight contact hypcrellipsoids.<br />
<strong>The</strong> hypcrellipsoid has the capability of producing<br />
shapes which resemble boxes with rounded corners-nol<br />
unlike modern cars and light trucks. Scparate ellipsoids<br />
and hyperellipsoids are used to represent the four whccls,<br />
the hood, trunk, roof, and body. <strong>The</strong> specific configura'<br />
'130<br />
6('<br />
40<br />
to<br />
o<br />
-20<br />
-{O<br />
-ao<br />
accclcrations, velocities, tnd displacements-both linear<br />
and angular.<br />
<strong>The</strong> ATB Vehicle Model been vnlidated for predicting<br />
the complex motion of a l9tt3 Dodge Aires which rolled<br />
four times during a tcst of highway barriers [14]. <strong>The</strong><br />
model has also been validatcd for predicting the motion<br />
of vehicles roll tcsted by thc NHTSA roll cart, <strong>The</strong>se<br />
tests involvc ejecting a vehicle from a test cart travcling<br />
at about 30 rnph. <strong>The</strong> longitudinill axis of the vchicle is<br />
approximately 90 degrees to the direction of the cart's<br />
motion. At the time of ejection, the vehiclc is flipped off<br />
by a hydraulic system, which imparts a roll velocity of<br />
approximately one revolution per second.<br />
<strong>The</strong> model uscd for occupant simulation is the ATB<br />
Occupant Model. This model is configured to reprcsent<br />
the occupant. <strong>The</strong> ATB Occupant Model has been extensively<br />
validated for prcdicting occupant motion in a<br />
crash. In thc case o[ rollover, thc AAMRL hits sitttulated<br />
numerous rollover tests frolrt the NHTSA rollovcr cart,<br />
thereby providing a body of validated data. A puhlished<br />
example of validatcd occupant motion in rollover is<br />
found in refcrence 15.<br />
Pure Roll Modeling of Occupants<br />
<strong>The</strong> influence of roll rfltc on the occupant was exam'<br />
ined using thc ATB Occupant Modcl. <strong>The</strong> data sct used<br />
was for a mid-size car similar to the one for which valid<br />
data is available in Rcl'crence [-5]. <strong>The</strong> roll rate was<br />
achieved by introducing a pure roll acceleration, similar<br />
to that produced by the NHTSA roll test cart. <strong>The</strong><br />
accelerltion was terminated whcn the desircd constant<br />
roll rate was achieved. <strong>The</strong> resulting occupant motion,<br />
and occupant to vchicle forces were thcn observed.<br />
Selccted results of simulations of a driver undergoing<br />
a countcr clockwise roll are presented in Figure 3. For<br />
this case, the prescnce of restraints has littlc influence on<br />
the occupant motion. <strong>The</strong> rcsulting forccs on the door<br />
and window for roll rates up to 3 revolutions per second<br />
are shown.<br />
FORCE ON DOOR/WINDOW fihousandg LBS.I<br />
;I<br />
o.5<br />
FOLL RATE . REV/$EC<br />
_ DOOR FORCE * WINDOW FORCE<br />
Figure 3. ATB Occupant Model--Foll Rate vs Force<br />
Exert6d by Occupant (Constant Roll Rate)<br />
t;<br />
g.s
Modeling of the Vehicle First Impact<br />
Many rescarchers have suggestcd that in rollover<br />
events, vehicle damage is an indicator of crash severity.<br />
An objective of the vehicle first impact modcling is to<br />
gain insight into relationships between vehicle damage<br />
and other crash parameters. <strong>The</strong> cstablishment of relationships<br />
betwcen velocity loss and vchicle damage<br />
would be useful in predicting the initial crash velocity.<br />
Thc model applied was the ATB Vehicle Model. <strong>The</strong><br />
data set used was that validated for the Dodgc Aries in<br />
a one rev/sec guardrail induced rollover at 60 mph [4].<br />
Four revolutions of roll cnsued. <strong>The</strong> vehicle stiffnesses<br />
were not changed from those in the base data set. <strong>The</strong><br />
values were inferred from comparing the model and test<br />
results.<br />
For the purpose of this sensitivity analysis, the vehicle<br />
initial position is an initial roll angle of 100 degrccs, and<br />
the roof is approximatcly I inch from touching the<br />
ground. From this initial condition, the following variables<br />
are independently varied: (l) lateral vclocity, (2)<br />
surface coefficient of friction, (3) roll ratc. <strong>The</strong> results<br />
are shown in Figures 4 through 6.<br />
<strong>The</strong> evaluation of vertical velocity is reported in<br />
Figure 7. In this Figure, vertical velocity is expressed in<br />
terms of the drop distance required to produce the vcrtical<br />
velocity. For this analysis, the vertical velocity wirs<br />
varied and the other initial conditions were constant. <strong>The</strong><br />
initial position was approximately 100 degrees, one inch<br />
above the surface. <strong>The</strong> initial latcral speed was 30 mph,<br />
and the roll rate was one rev/sec. <strong>The</strong> vertical velocity<br />
was varied through a change in initial vclocity, not by<br />
changing the initial position.<br />
Analysis of Accident Cases<br />
In order to gain information from accident cases, a<br />
detailed analysis was conducted of 140 rollover cases<br />
from the 1988-89 NASS filcs. <strong>The</strong>se cases were sclected<br />
to rcpresent those with significant vehicle damage.<br />
Attempts were made to verify the initial speed, to<br />
determine the nature and extent of thc tripping mechanism,<br />
and to estimatc thc initial roll rate.<br />
Thc results of the study are incomplcte. However, estimates<br />
of the roll rates suggest that the maximum roll rate<br />
observed is in the order of 2.5 to 3 rev/sec. <strong>The</strong> estimates<br />
are based on vehicle and scene evidcnce including<br />
initial velocity, distance between trip and initial impact,<br />
and vehicle angular rotation between Fip and first<br />
impact.<br />
Discussion of Results<br />
Thc results presented are based principally on computer<br />
simulation. In these simulations, the crash evcnts<br />
in tripping, pure roll, and first vehicle impact are<br />
separated and analyzes indepcndently. <strong>The</strong> objective is<br />
to explore how pivotal parameters which influence crash<br />
severity interact in each phase of the crash.<br />
Sectlon 3: Technlcel Sessions<br />
VELOCITY LOSS - MPH ROOF ORUSH - IN<br />
*[<br />
6<br />
'r<br />
4f<br />
3r<br />
2r<br />
rf<br />
oL<br />
20<br />
-<br />
LATERAL VELOCITY - MPH<br />
VELOC|TY LOSS * ROOF CRUSH<br />
Figure 4. ATB Model-Lateral V€locity vs. Velocity Loss<br />
and Roof Crush (1 rev/sec Roll Hate)<br />
VELOCITY LOSS - MPH ROOF CRUSH - IN<br />
5r<br />
5<br />
;l<br />
4<br />
3<br />
2<br />
0. 6<br />
-<br />
o.8 1<br />
FRICTION COEFFICIENT<br />
VELOCITY LOSS + ROOF CRUSH<br />
Figure 5. ATB Model-Surface Friction vs. Velocity Loss<br />
and Rool Crush (1 rev/sec Holl Hate)<br />
VELOCITY LOSS . MPH<br />
B<br />
ROOF CRUSH - IN<br />
B<br />
5<br />
5<br />
4<br />
4<br />
3<br />
3<br />
2<br />
2<br />
I<br />
1<br />
o<br />
0 1 2<br />
ROLL RATE - REV/SEC<br />
3<br />
0<br />
4<br />
-<br />
VELOCITY LO$S + ROOF CRUSH<br />
Figure 6. ATB Model-Roll Hate vs. Velocity Loss and<br />
Hoof Crush (30 mph Lateral Velocity)<br />
VELOCITY LOSS. MPH<br />
ROOF GRUSH - IN<br />
0.5 r l,s 2 2.5 3<br />
DROP DISTANCE (FT.)<br />
- VELOCITY LO$S * ROOF CRUSH<br />
Figure 7. ATB Model-Vertical Velocity vs. Velocity Loss<br />
and Foof Crush (1 rev/sec; 30 mph Lateral Velocity)<br />
. ! j<br />
5<br />
4<br />
3<br />
2<br />
1<br />
I<br />
o<br />
,.8<br />
',f<br />
ji<br />
':<br />
fit<br />
ft<br />
1<br />
'i<br />
,t<br />
g<br />
i{<br />
a<br />
I<br />
{<br />
jj<br />
.!<br />
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73t 1<br />
.n<br />
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i
lSth lnternetlilnel Technlcal Conterence on Experlmental Sefety Vehlcles<br />
Dala analysis by Malliaris has idcntified initial vclocity<br />
as a pivotal paramcter in rollovcr crashes. Thc STI<br />
model suggests that roll rate is strongly relatcd to initial<br />
velocity for trippcd rollover (Figures I & 2). <strong>The</strong><br />
tripping mechanism simulated by the STI modcl may be<br />
more severe than seen in high speed rollovcr crashes.<br />
<strong>The</strong> roll rates predicted by lhe STI modcl were in exccss<br />
of 5 revlsec for the rangc of crash spccds which account<br />
for 507o of thc rollovers. However, analysis of NASS<br />
rollover data suggests that roll rates above 2.5 rev/sec<br />
arc rare.<br />
<strong>The</strong> high tripping forces permitted by the STI model<br />
may account for this disparity. Nevcrtheless, the the<br />
strong relationship between linear velocity and roll<br />
vclocity, is worthy of furthcr investigation and verification.<br />
<strong>The</strong> pure roll simulations show that high roll rates,<br />
indcpendent of othcr impacts, can produce conditions to<br />
induce ejection (Figure 3). <strong>The</strong>sc results indicate that in<br />
pure rolls, the occupant forces on the door and window<br />
can cxceed 1000 pounds at roll rates of 2 rev/sec. This<br />
load is gcncrally sufficicnt to causc glass breakagc. At<br />
2.5 rev/scc the force on the can door exceed 2500 lbs.<br />
By way of comparison, the Federal Motor Vehiclc 'Safety<br />
Standard on door latch strength rcquires a 2500 lh. test.<br />
<strong>The</strong>se simulation results suggcst that high values of roll<br />
rate may have a profound influence on the potential for<br />
ejection.<br />
<strong>The</strong> correlation between ejection and number of<br />
quarter turns of roll which is reported in the literature<br />
has been postulated to be related to incrcased time of<br />
exposure to the risk of ejection. However, thc modeling<br />
suggcsts that the increased severity of the roll rate may<br />
also be a dominant factor.<br />
<strong>The</strong> acceleration produced by the initial tripping<br />
acceleration can have a profound influcnce on the<br />
position of thc occupflnt prior to the time the rollovcr<br />
begins. For example, in tcsts reported by Hahberstad [3],<br />
thc tripping irnpacl produced sulficient acccleration to<br />
eject the occupant prior to rollover. For ntany roll<br />
configurations, the tripping accelcratiolt ilcts to mitigate<br />
the initial roll acceleration. This interaction an importflnt<br />
part of the accident data analysis, and occupant modcling<br />
studie$ which are currcntly underway.<br />
<strong>The</strong> simulations of first vehicle impact providc insight<br />
into those variables which influence roof crush and<br />
vclocity loss (dclta-V). <strong>The</strong> condition simulated was a<br />
mid-size vehiclc impacting on its roof at a roll rate of<br />
one revolution per second. In the validating test for this<br />
simulation, the test vehicle roof was not grcatly damaged.<br />
As a result, the parameters do not recognize the<br />
failure characteristics of the structure. Results may be<br />
considered as indicators of trends, but should not be<br />
considcrcd as absolutc.<br />
<strong>The</strong> simulation shows that roof crush and roll vclocity<br />
loss are largely indcpendent of lateral velocity (Figure<br />
4). <strong>The</strong> implication of this result is that high spccd<br />
732<br />
testing may not be needed to evaluate high speed<br />
protcction in rollovcr crashes.<br />
Coefficient oI surlace friction has negligiblc influence<br />
on roof crush, but a significant influencc ort vclocity loss<br />
(Figure 5). This result is intuitively tppcaling.<br />
Roll rate scnsitivity is shown in Figurc tr. At high roll<br />
rates, some rotational energy is transl'erred to translational<br />
cnergy during impact. Consequently, thc translational<br />
velocity loss dccrcases with incrcasing roll rate.<br />
Roof crush is relatively insensitive to roll rate.<br />
Vertical velocity, exprcssed in tcrms of drop height is<br />
shown in Figure 7. Thc results show that the vcrtical<br />
velocity has a strong intluence on both the roof crush<br />
and velocity loss.<br />
One of thc objectives of this research is to provide<br />
guidancc to crash invcstigators. Ultimatcly it is desircd<br />
to assess crash scverity fron tlrc damage to thc vchicle.<br />
For the conditions examincd, vehicle damage was influenced<br />
most by verticrl vclocity, nol roll rflte or lateral<br />
velocity. <strong>The</strong> only basis found for eslimating roll rate<br />
and horizontal vclocity wils from nreilsurcnlcnts of impact<br />
locations ilt Ihe crash sccnc.<br />
Adrtitional dala collection elcments will be rcquired to<br />
evaluate the signiticilnce of thc tripping mcchanisnt, the<br />
roll rate and the vertical vclocity on rollover crash<br />
severity.<br />
References<br />
l. Cohen, D., Digges, K., and Nichols, H., "Rollover<br />
Crashworthiness Classification and Sevcrity<br />
Indices," l2 ESV Conl'crcnce, Papcr Nr. 89-28-0-<br />
012. May 1989.<br />
2. Malliaris, A, and DeBlois, H., '*Pivotal Characterization<br />
of Rollovcr," Procecdings of the l3tlt ESV<br />
Confcrcnce,1991.<br />
3. Habberstad, J., Wagner, R., and Thomas, T., "Rollover<br />
and Intcrior Kinematics Test Procedures<br />
Revisitctl," Procecdings of 30th Stapp Conference,<br />
sAE rt6ln75. 1986.<br />
4. Orlowski. K.. Bundorf, and Molfatt, E., "Rollover<br />
Critsh Tests-Thc lnfluence of Roof Strength on<br />
Injury Mechlnics," SAE 851734.<br />
5. Robertson, L., and Kelly, 8., "Static Stability as a<br />
Predictor of Rollover Crashcs Fatal to Occuplnts of<br />
Cars and Utility Vehiclcs," Journal of Trauma.<br />
6. Robertson, L., "Risk of Fatal Rollover in Utility<br />
Vehiclcs Rclative to Slirtic Stability," Prcscntation to<br />
1988 SAE Govcrnntcnt/Inclustry Mccting, May 3,<br />
1988.<br />
7, Harwin, A., and Brewer, H., -'Analysis<br />
of the Relationship<br />
Belwcen Vehicle Rollover Stabilily and<br />
Rollovcr Risk Using NHTSA Cardfilc Accidcnt Data<br />
Brsc," NHTSA Intcrim Report, 1987.<br />
8. Malliaris.. A.. --Rollover<br />
in Motor Vehicle Accidcnrs,"<br />
NHTSA-TSC-HS078- 1, July, 1 989.
9. Mengert, P., Salvatore, S., DiSrrio,R., and Walter,<br />
R.,<br />
10.<br />
"Statistical<br />
Estimation of Rollover Risk," DOT-<br />
HAS-807-446, August 1989.<br />
Harwin, A., and Emory, L., "<strong>The</strong> Crash Avoidance<br />
Rollover Study: A Database for thc Investigation of<br />
Single Vehicle Rollover Crashes," NHTSA Intcrnal<br />
Rcport, May 1989.<br />
Rosenthal, T. J., et.al., "Users lt.<br />
Guide and Program<br />
Description for a Tripped Rollover Vchiclc Simulation,"<br />
STI Document l2l6-?, Contract DTNH-84-D-<br />
17080. June. 1985.<br />
s6-o-06<br />
Manufacturer's Overview of Rollover<br />
Robert L. LeFevre, Richard E. Rasmussen<br />
General Motors Corporation<br />
Abstract<br />
Rollover accidents are flmong the most difficult of the<br />
major accident categories to analyzc through the application<br />
of full-scale test proccdures. Because o[ this<br />
difficulty, industry and govcrnmcnts worldwide have not<br />
rcachcd a consensus on a full-scalc lcst technology to<br />
asscss a vehicle's ability to rcsist rollover motion.<br />
Additionally, progress in developing tcst procedures to<br />
define rollovcr resistance has heen rctrrdcd by the<br />
factors of accident complexity and a rcluctance to<br />
separatc mancuver handling issues from those specifically<br />
related to thc rollover event. <strong>The</strong> relevancc of<br />
field accident data to lcst procedure $election will bc<br />
descrihed with cxamples from U.S. expericncc. Candidate<br />
procedures from around the world will bc discussed<br />
and a sct ofcriteria forjudging and conrparing lhc mcrits<br />
of thesc proposals will be suggested. All proccdurcs<br />
represent compromises between the desire to include<br />
every contrihuting factor and a need to distinguish<br />
differences in rollover performancc. Also, problems<br />
associaled with validating candidale procedurcs with<br />
field accident data are describcd.<br />
Introduction<br />
Since the earliest days of the automotive industry, the<br />
role of vehicle design in rollover accidcnts has bcen<br />
intensively invesligated as pictured in Figures I and 2.<br />
Many improvemcnts in body structure, chassis contponent<br />
integrity, tire bead relention. mass distribution, and<br />
pas$enger restraint systcms hirve bcen introduced as<br />
passcngcr car and light truck designs have evolvcd. This<br />
evolution will continue as light trucks movc towilrd indepcndcnt<br />
front suspensions for all wheel drive configurations.<br />
Indepcndcnt lront suspensions will pennit lower<br />
powertrain componcnts, hcnce, the lowering of center of<br />
gravity hcights.<br />
Sectlon 3: Technlcal $esslons<br />
12. Nalecz, A.G., et. al., "Scnsilivity Analysis of<br />
Vehicle Trippcd Rollover Model," NHTSA Report<br />
DOT HAS 807 3(X) July, 1988.<br />
13. Garrott, W. R., and Monk, M. W., "Vchiclc Inertial<br />
Paramctcrs, Mcasured Values and Approximations,"<br />
SAE Paper 881767, Novcmbcr, l9tl8.<br />
14. Kalcps, I., and Rizer, A., '-Sinrulalion<br />
of Vehicle<br />
Crash and Rollover Dynamics," NHTSA Report<br />
DOT HAS 807 049. Junc. l9lJ6.<br />
15. Obergefell, L. A., ct. al., "Prediction<br />
of an Occupant's<br />
Motion During Rollover Crashes," SAE Paper<br />
861rt76. 1986.<br />
Resistance Test Technology<br />
Figure 1. Early Center of Gravity Height Test Facility at<br />
the GM Proving Ground<br />
Figure 2. Early Lateral Rollover Test on Level Ground at<br />
the GM Proving Ground<br />
However, vehicle dcsign is not the only consideration<br />
in rollover rccidcnt preventiun. Of cqual or grciltcr<br />
733
lSth lntemetlonal Technlcal Conterence on Experlmentel Setety Vehlcles<br />
importance in rollover prevcntion are design improvements<br />
for roadsidc gcomctries and barrier systems Ill.<br />
Furthcr, statistical analysis of accidcnt data provides a<br />
wealth of information on the dominant role of driver<br />
impairmcnt and demographics in this spccial class of<br />
accident.<br />
Despite considerable public and private sector attention,<br />
significant gaps remain in the technology of fullscale<br />
vehicle rollover perfonnance evaluation. Thcrc are<br />
no objective test procedures that have reccivcd worldwide<br />
industry and govcrnment acceptance for evaluating<br />
the ability of a dcsign to resist rollover during a prccrash<br />
maneuver. In fact, there are nearly as many lcst proposals<br />
as investigations into the $ubject. Among the<br />
factors retarding progress in identifying an agreed upon<br />
test procedurc arc the complexity of the rcal world event,<br />
the difficulty in isolating a vehiclc's resistance to<br />
rollover from driver and road-environmcnt issues, and<br />
the problems associated with drawing appropriate conclusions<br />
from trends suggested by thc accident data.<br />
This paper providcs an evaluation and comparison of<br />
candidate rollover resistance test procedures and<br />
examines the basic compromises that may be inherent<br />
with the availablc choices.<br />
System Overview<br />
<strong>The</strong> three-clcment, closed-loop systcm illustrated in<br />
Figurc 3 is essential to every analysis of rollover ovcnts.<br />
Each clcment needs to be factorcd into l) evaluation oI<br />
field accidcnt dflta, 2) assignment of causation resp()nsibility,<br />
or 3) comparison of objectivc tcst procedures.<br />
Totally focusing on one elemcnt, excluding the othcr<br />
two, has led to conclusions and recommendations that<br />
are misleading. For development of objcctive test<br />
procedures that are intcndcd to define the vehiclc's role<br />
in the rollover event, it is absolutely necessary to<br />
consider the driver and road contributions in order to<br />
control or eliminate thcm.<br />
Figure 3. Control System fror Hollover Analysis<br />
This three-clement, closed-loop system is conccptually<br />
simple and has been modeled with a degrcc of success<br />
for many years. Howcver, the properties of the drivcr<br />
't34<br />
and road components as elements of a control systcm<br />
must be viewed as nonlineur, stochastic, and lacking in<br />
thc important propcrtics of stationarity and ergodicity<br />
that are basic assumptions for conventional systetns<br />
analysis. Few statistical parameters describing thc<br />
performance of these stochrstic control elements ilre<br />
tabulated in thc litcrature and the linited availablc data<br />
show widc rangcs: driver control strength has bccn<br />
observed to vary over a range of four-to-one, surprise<br />
reaction time can vary by six-to-one, and road friction<br />
can vary by ten-to-one with even broader rangcs of<br />
spectral content in road profiles.<br />
Recent studics of large accidcnt data filcs are<br />
beginning to dcnronstrate il hrge degrcc of interdependence<br />
in thcsc thrce basic system clcmcnts. For<br />
examplc, a particular vehicle design is not cxposed to a<br />
random selection of drivcrs, nor is it operatecl in a<br />
randomly selccted portion of lhc availablc road environmcnt.<br />
Rollover accident rates evidcnt from licld data for<br />
particular vehicle dcsigns flrc not necessarily the result<br />
of thc dcsign, but are strongly influcnccd hy thcse driver<br />
and road-environlnent elements. Thcsc influences must<br />
bc uscd in correlating rollovcr rcsislancc test results with<br />
field accidcnt data.<br />
Test Selection Criteria<br />
Two lactors influcncc industry views on thc ntost<br />
appropriate approach to measure rollovcr rcsistance of a<br />
vehicle design.<br />
. Historicrlly, automotive testing has been comparativc<br />
in nirlure. Engineers and dccision makers want<br />
to know how Vehicle A cornparcs to Vehicle B with<br />
confidence and prccision, particularly where regulatory<br />
compliance margins are involved.<br />
' Accident data show thilt all vchicles experience rollover<br />
rcgardlcss of their size and mission.<br />
<strong>The</strong>refore, industry is most intcrested in test procedures<br />
which rre caltablc of assigning numbers to product<br />
perforrnance with distinguishable resolution and having<br />
the hroadest possible applicability. At a minimum, il test<br />
proccdure would be expcctcd to encompass the full rlnge<br />
of light duty vehiclcs. It is rccognized that heavy lrucks<br />
and articulated vchiclcs often require test proccdurcs<br />
which are tailored to their special chuacteristics and use.<br />
Other considcrations that intluencc industry views on test<br />
proccdurcs arc:<br />
. Field Relevance-<strong>The</strong> test should comprchcnd phenomena<br />
thrt contribute to field performance to the<br />
greatest extent possiblc.<br />
. Performance Critcria-<strong>The</strong> test should producc performance<br />
on a continuous rating spectrum, rather<br />
than just provide a pnss/tail tneasute.<br />
' Reproducibility-<strong>The</strong> test should be ctpablc of being<br />
run s() that different laboratories obtain thc same<br />
results, particularly in lhc context of regulations.
' Responsiveness*Tte test should be relatively short<br />
in duration and low in cost to help with the rapid<br />
pace of automotive developments.<br />
. Computer Modeling-While virtually all physical<br />
$ystcms can be modeled, the resources required to<br />
model some situalions can exceed those associated<br />
with full scale testing of prototypes. <strong>The</strong>se situations<br />
need to be avoided where possible.<br />
. Low Risk and Nondestructive-<strong>The</strong> test should pose<br />
minimal risk to the safety of personnel and result in<br />
minimal damage to expensive prototype vehicles.<br />
Accident Data Issues<br />
Several levcls of government in the Unitcd States have<br />
compilcd a numher of extensive accident data files over<br />
the past decade. <strong>The</strong>se files vary from special purpose<br />
files containing about 1000 reports, to one very large<br />
general purpose file with over 6 million reports. <strong>The</strong><br />
quantity and quality of the information in each of these<br />
files varies with the siee and intended purpose of the<br />
file. As the following paragraphs will explain, it is<br />
esscntial that information in these filcs be applicd to the<br />
problem of selecting appropriate rollovcr resistance test<br />
procedures.<br />
Figures 4 and 5 depict rollover accident statistics for<br />
passenger cars and light trucks from the National Accident<br />
Sampling System (NASS) file which consists of<br />
samples of severe accidents that occur on U.S. roadways.<br />
Several relevant findings are immediately evidcnt from<br />
this most simple array of accident statistics:<br />
' Pni.Gdilr ts.d ff tokr rWrd rctld*<br />
hrhi{ rt d ft ldd4: tt||y, lrdld<br />
r.ilit lniury ru uF|fffi b lslbl {<br />
Yrtich lord froh *fta.<br />
Figure 4. Pestenger Car Rollover Prolsctionr Based on<br />
1986 NASS Datr<br />
' Proiectionc h|$d on Foh rrpdd GH.Ib<br />
invdenl .nt d ft ltuhl: ltily, Hl..L<br />
hd|ll Iniury pereon ril4ffi b ifllbl or<br />
{ilch iored ton $m.<br />
Figure 5. Light TrucldVan Rollover Nstlonal Profections<br />
Besed on 1986 NASS Data<br />
:- Sectlon 3: Technlcal $essfons<br />
. Rollover accidents ,*fr*r*nt a small portion of the<br />
total speclrum of vehicle accidents, even at the<br />
rclatively high level of severity rcpresented by the<br />
NASS file.<br />
' Rollovers on the roadway represent a very small<br />
portion of total rollover accidents.<br />
. <strong>The</strong> most prevalent rollover accident scenarios are<br />
off-road and multiple vehiclc collisions which are<br />
often thc most complicated.<br />
. Rollover accidents nre a higher portion of all light<br />
truck accidents than is the case with pilssenger cars.<br />
It should be noted that this finding may reflect a<br />
lower prevfllence for other classes of light truck<br />
accidents.<br />
In the U.S., there has been considerable publicity and<br />
literature about the rollovcr rates for sport utility<br />
vehicles. Figure 6, rcproduced from a 1990 NHTSA publication<br />
on light truck safcty, implies a rapid and<br />
unexplaincd reduction in rollover fatality rales for this<br />
class of vehicle for a four year period from 1985 to 1988<br />
[2]. Rollover filtitlity rates lor sport utility vehiclcs<br />
during 1988 werc slightly lowcr than those for small<br />
pickup trucks according t
lSth lntematlonal Technlcal Conference on Experlmental Sefety Vehlcles<br />
- Ar BrCr Dr Er Fc GcHc lr Jc Kr LrMr NrOr Pr Qc Rr<br />
I:H'J"<br />
Figure 7. Fatal Rollover Evente Per 10,000 Registered<br />
Vehicle Years; Single Vehicle Accidente<br />
(1e8+87 FARS Deta)<br />
. One third of the top half of this sample's rollover<br />
rates belong to sporty cars, these being the lowest<br />
and widest vehicle dcsigns operatcd on public roads.<br />
<strong>The</strong> driver factors recorded lor the vehiclcs and accidents<br />
of the sample are summarized in Figures 8(a), 8(b),<br />
and 8(c) [3]. Driver age demographics varies by a factor<br />
of six; alcohol involvement varics by a factor of three;<br />
and poor driving records also vary by a factor of three.<br />
<strong>The</strong> low, wide sporty cars consistently make up one third<br />
or more of thc vehicles in the upper half for each driver<br />
category.<br />
100<br />
80<br />
To 60<br />
Drivers ag<br />
20<br />
0<br />
iloTE: Frcehrrff<br />
compurEd rion drrv€re wirh kmwtr no enry<br />
I : HS"<br />
Figure 8(a). Percentage ol Drivers Less than 25 Years ol<br />
Age (198tL87 FARS Data)<br />
100<br />
80<br />
% 6 0<br />
Drivers<br />
49<br />
20<br />
o Kr Oc Br Gc Er Lr lr Hc Gr14 N, D, Or Ar Rr Jc Fc pr<br />
NorF. p,rconriqo compurod froh drivlrj wilh xnown bhd Ercohor r.v.rs onry<br />
Flgure 8(b). Frrcentage ot Drlvers With Blood Alcohol<br />
Above 0.1ol. (198+87 FARS Data)<br />
736<br />
Lr Fc Jc ll Er Hc cr Gc Drlq B, N, Ar Pr Kr Rr Or Qc<br />
l:<br />
*:j"<br />
100<br />
80<br />
Yo 60<br />
Dilvets<br />
46<br />
Qc Lr lr G. F" K, Cr Hc Pr Br Jc Er Mr Dr Or Nr Ar Rf<br />
NorF: pcr+ed'F coilpurod rroh drivc' wirh rnown mords onry<br />
I : Hj'<br />
Figure 8(c). Percentage of Drivers With Prior Speeding<br />
Convictlon (198+87 FARS Data)<br />
Similar characteristics are evident in available data on<br />
environmental factors and rollover. Figurc 9 illustrates<br />
the range in rollovcr rates for castern urban ccnters as<br />
compared to western mountain stalcs in the U.S. [4].<br />
Neglecting thc District of Columbilr, thcrc is a factor of<br />
five in this comparison of rollover riltes bctwcen states.<br />
Figure 9. Hollover Flates by Geographic Location<br />
<strong>The</strong> above few excerpts from the very extensive rollover<br />
accidcnt datil litcraturc are quoted hcrc as a caution<br />
for thosc who flttempt to validate rollovcr rcsistance test<br />
proposrls from raw rollover rates derivcd from field<br />
data. Whilc it rnay be possible to ernpirically model the<br />
rollovcr situation from lhe large body of accident<br />
information that has been collectcd, thcse few findings<br />
dcmonstrate that causation modcls ntust contain fl<br />
balancc of driver. vchicle, and environmcnt factors in<br />
ordcr to represent thc situation for confidcnt identification<br />
and extraction of vchicle factors.<br />
Test Procedure Proposal Categories<br />
Sincc there are rnilny proposals for test proccdures to<br />
measurc a veh iclc's ability to resist rollovcr, it is<br />
appropriate to crcate categories of these proposals so<br />
they can be discussed and compared in an organized<br />
manner. <strong>The</strong> calcgory system uscd in this paper is as<br />
follows:
' Physical Properties Tests-<strong>The</strong>se are laboratory tests<br />
intended to measure basic physical properties with a<br />
conceptual rclationship to rollover resistance.<br />
. Rollover Simulations-<strong>The</strong>se are also laboratory<br />
test$ intcnded to estimate, compirratively, thc lcvcl<br />
of maneuver severity that a vchicle can achieve at its<br />
threshold of rollover.<br />
. Dynamic Road Tests-This category includcs all<br />
procedures that involve operation of a vchicle on a<br />
roadway. Since many of the procedurcs thal have<br />
been publicized are ad hoc evaluations conducted by<br />
magazines, these proccdures are usually not as<br />
specified nor as documented as those conducted by<br />
automotive testing organizations. For purposes of<br />
this paper, the general problcm of dynamic road<br />
testing for rollovcr performance will bc discussed<br />
without detailed referencc to specific procedurcs.<br />
P hysical Propertie s Tests<br />
Analysts and modelers generalty ngree thflt three<br />
vehicle properties lre fundamental factors in rollovcr<br />
equations of motion: I ) track width, 2) center of gravity<br />
height, and 3) roll moment of inertia. <strong>The</strong>re are adclitional<br />
important factors that have not received the<br />
attention from investigators inside and outsidc the<br />
transportation industry which are outsidc the scope of<br />
this paper.<br />
Figure 10. Test Facility Used to Measure Center of Gravity<br />
et the GM Proving Ground<br />
27U 27.4<br />
?8.1! 2tJ<br />
18.19<br />
ti<br />
2(?l A.!<br />
nl5 27.19 S.! tG.tt<br />
ro 16.?t ?5.m 6.S<br />
tr$ z5,n 2{.9 ?a.ff<br />
?.0r ?376 ?t.fl n.$<br />
15.7? ?5.S 2t?t 6.13<br />
?7.8 6,$<br />
?a.g a.E<br />
28.24 A5l<br />
3rj1.' E-g<br />
24.0t 24f,<br />
Averag€<br />
C,G. H€lght<br />
(lnches)<br />
26.0<br />
n.o<br />
2S.0<br />
26.0<br />
e4.o<br />
23-O<br />
zL.o<br />
veh.t veh,2 veh.3 Buck<br />
Flgure 11 . Center of Grevity Measurement by Laboretory<br />
' I Sectlon 3: Technlcal Sessfons<br />
While roll moment of incrtia is a physical factor that<br />
should relatc to a vehicle's ability to resist large<br />
transient latcral forces associatcd wilh curb impact and<br />
soil mechanics, it has rcccivcd lcss rnedia ailcntion than<br />
c.g. location. Many ilutolnotive laboralorics have facilities<br />
for measutcmcnt of whole vchiclc momcnts of<br />
inertia because they arc fundlmental to a vtricty of<br />
dynamic pcrformrrnce modcling flclivities. A roll nroment<br />
o[ incrtia test facility is shown in Figure 12. Such<br />
facilities are configured so thtt vchicle inertia magnitude<br />
contributes directly to lhe period of a simple rnd predictablc<br />
oscilhting systern. Thc pcriod of oscillation,<br />
measured with grcal precision is proporlional to the<br />
moment of inertia where thc c.g. location is known and<br />
appropriate mathematical axes conrpcnsation hns been<br />
accomplished. <strong>The</strong> facility in Figure l2 holds thc vchicle<br />
on a platform supported hy knitc cdges and springs.<br />
Other facililies usc air bcaring supports or multifilar<br />
pendulum systems. Roll moment of incrtia, for ptsscnger<br />
cars, has bccn found to be a simple function of vehicle<br />
total mass rnd dimensions [6]. It can often be predicted<br />
cmpirically fronr thcsc properties with an acceptable<br />
dcgrcc of precision. Similar formulas for light trucks nrc<br />
not availahle, Thc tulhors are unawarc of any investigation<br />
to cstrblish repeatability or correlation bctwccn<br />
industry ftcilities for incrtia meflsurement. Usc of large,<br />
simplc Structures with nrass and geometry approaching<br />
that of vchicles and inertia propcrtics thilt are readily<br />
calculated can bc hclpful in validation of inertia test<br />
facilitics.<br />
Figure 12. Roll Moment of lnertia Test Facility at the GM<br />
Proving Ground<br />
Rollovcr Simulalions<br />
<strong>The</strong> rollover simulation laboratory tests most often<br />
discussed for measurenrcnt of rollovcr rcsistunce use the<br />
tilt table and sidepull procedures. Of these, the tilt table<br />
test is thc most widely used around thc world beciluse it<br />
accornrnodatcs it broild range of vehicles. <strong>The</strong> tilt tablc<br />
procedurc is viewcd as simple and modcst in cost. Two<br />
factors sccm to support usage o[ this tcst:<br />
737<br />
d<br />
rt<br />
1I<br />
riE<br />
a<br />
il<br />
.J<br />
4 ?:<br />
j<br />
:<br />
d<br />
{<br />
i<br />
:i<br />
'a<br />
,*<br />
q<br />
r!<br />
n<br />
d<br />
s :H<br />
j<br />
:E<br />
I
l?th lntematlonal Technlcal Conference on Experlmentel Safety Vehlcles<br />
. Field data shows that operation on a sideslope to bc<br />
thc most prevalent rollovcr accident circumstance<br />
such as may be the case with earthmovers and hcavy<br />
lrucks.<br />
. A need to evaluatc or regulate rollover rcsistance for<br />
the least stable portion of the vehicle population,<br />
, such as double decker buscs, articulated tanker<br />
lrucks, three-wheeled passengcr cars and threewheeled<br />
light commercial vehicles.<br />
Many four-wheclcd passenger cars and light trucks<br />
initiate rollover only in response to high levels of latcral<br />
force. For these vchicles, the tilt tablc approach may<br />
havc limitations or lack credibility. Wherc the lateral<br />
forcc required to initiatc rollover begins to approach the<br />
weight of the vchicle, very large tilt angles are necessary<br />
for whccl lift. For these cases, the vehicle suspcnsion<br />
will move to full rebound, the tires will bccome lightly<br />
loaded and difficult to restrain as thc anglc for wheel lift<br />
is approached. Some proponents of the tilt tablc conduct<br />
the tcst at maximum cargo load to lowcr the tilt ilngle<br />
required for wheel lift. While this stratcgy may make the<br />
test easier to obtain credible results for passengercarrying<br />
light trucks with large cargo capacitics, the<br />
influence of cargo may not be sufficient for testing<br />
sporty cars and other vehicles with small capacity.<br />
In addition to the above difficulties, the tilt table test<br />
procedure also does not comprehend that lateral rollovers<br />
are often a result of tripping. Accident investigators in<br />
the U.S. have concluded that tripping for a broadsliding<br />
vehicle is the most prevalent rollover circumstance encountered<br />
in light vchicle accident reconstruction activitics<br />
[7]. Figure l3 provides statistics that support this<br />
conclusion [81. <strong>The</strong> road cnvironment in othcr parts of<br />
the world may increase the prcvalence of sideslope as a<br />
dominant factor in rollover accidcnts. However, in the<br />
U.S. this is not the casc.<br />
o/o of Rollovers<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
o<br />
Mechanism<br />
Figure 13. Initiating [t/lechenlem In U.S. Rollover<br />
Accidents<br />
0lhor/<br />
Unknown<br />
Recognizing the limitations of the tilt table test and<br />
the long, frustrating and nonproductive experience with<br />
dynamic road tests, investigators in the U.S. began to<br />
look for a hybrid lab/road test that would combine the<br />
advantages of lab testing with thc rcalism of road tcsting.<br />
A cable was used to pull on thc side of a moving vehicle<br />
738<br />
Pavement Dllch Soil,Flat<br />
Edge<br />
Guardlail<br />
Embsn[.<br />
mnU<br />
Sl0p6<br />
to determine the lateral force requircd for two wheel lift.<br />
<strong>The</strong> cable was mounted from a heavy truck to provide a<br />
sufficient and stable reaction for this test. Some test<br />
facilitics used rail mounted vchicles or tracked vehicles.<br />
While the variability in tirc-road friction made this<br />
approach to rollovcr resistance testing impractical,<br />
investigators nolcd that lateral force for two wheel lift<br />
for a rolling vehiclc was virtually identical to lcvels for<br />
a nonrolling vehicle. Subsequent tire testing rcvcalcd that<br />
tire vertical and lateral spring rate.s, for thcsc severe<br />
conditions, rolling and nonrolling, are very similar whilc<br />
many other tire propcrtics are significantly difterent.<br />
Since tire vertical spring rate and lateral spring rate<br />
(more properly termed oycrturning Inoment) arc among<br />
thc major tire factors contributing to rollover rcsistance,<br />
this finding suggested that il nonrolling laboratory sidepull<br />
test might provide a prccise measure of rollovcr<br />
resistancc where broadslidc rclated tripping is known to<br />
be a most prevalent rollovcr accident circumslancc.<br />
A facility for this purposc is shown in Figure 14. <strong>The</strong><br />
vehiclc is pulled latcrally with a meilsured force that is<br />
controllcd to be horizonlnl, oriented at ninety dcgrees to<br />
the plane of syntmctry, and nrrtngcd to pass through thc<br />
gravity center localion as it movcs vertically as a rcsult<br />
ot the lateral forcc. This is accomplished with simplc<br />
closed loop controls that sense ccntcr of gravity hcight,<br />
cable angle, and vehicle yaw motion. Rato of incrcase in<br />
the pull force is slow 1o result in a tcst that is essentially<br />
steady stilte. Vchicle restraint is assured with a low curb<br />
restrilint of the tire. Inncrtubes are used to prcvent tire<br />
bcad unseating and air loss for these cxtrcnle conditions.<br />
A sling is used for most cars and lrucks to spread the<br />
pull forcc and minimizc body damage. Thc tcst is replicated<br />
six timcs to provide resolution in the range of 0.02<br />
for the sidepull ratio which is thc ratio of lateral forcc at<br />
two wheel lift versus vchicle test weight. This would<br />
correspond to test rcsolution of 0.02 G's il this situation<br />
could be rcproduced with a road milneuver test.<br />
Figure 14. Side PullTe$t Facility at the GM Provlng<br />
Ground<br />
This tcst has heen used for some years on a varicty of<br />
pflsscnger cars, light lrucks, and sport utility trucks.
Secilan i: Teehntcat Sasslons<br />
ffli:";-liftr:::jillil"",fiT::',[TJ:1iff,.:ff:,fj<br />
::i,.:n record ",,n,,11:r1,:rions experienced in pursuin<br />
are that the approach. has so<br />
light<br />
#il;;;pdicabre<br />
duty vehicte submitted<br />
to every<br />
r".",.ritre<br />
in thc u's'<br />
onry<br />
are k11yn<br />
rhrce rabs<br />
t" ;;;;'";;'r'hi, p.orrdure and<br />
a controlletl and rcpeatab.t. opp.o,,""n<br />
of this<br />
rui'h"e<br />
work<br />
resting.<br />
was prohabty<br />
Most<br />
i;;r;;J<br />
occupilnl f*<br />
prorecrion,<br />
evaru.rion of<br />
bui ,iriror- airricurries wcre<br />
lit'f*J:+".'ffiiiilil'#Ilill;:mi;ffffl#<br />
may<br />
.v-rqu<br />
be iif:il1'JJ,1HiH::,il*'fl!r*<br />
assttciated<br />
LUrrcrarloll<br />
*.irt ..g.<br />
rollover<br />
t".;;;;.<br />
resistance road rcsrs l; ;;';ffilr; afrer mosr<br />
,"'lh."-o:ll;1"i:T;'.i'.?lii.m,l*rildilI"ff<br />
dynamics.<br />
,"f, t'il_j1;#ilil"Tlf [T-'";;t*##"<br />
For example,, n*irr,*i-if,J-.io*pull<br />
table test results<br />
nor the<br />
ar-e influenc*,r<br />
tilt<br />
momenr<br />
ly'l.r,icte<br />
of inertia'<br />
rott<br />
It<br />
axis<br />
mry<br />
rnore<br />
ue po#tte<br />
sophisticatcd<br />
to consrru.t<br />
sidepull<br />
a<br />
,"ri-,r*"i." ,r,oi *oulo-<br />
|iilt l"'ilil"i::1,,n;1-r;f1-.<br />
-i^o ijet., ,i'* ,o*-;<br />
'Ability to preci.sety.rlefjne the<br />
maneuver<br />
severity<br />
ihar<br />
of<br />
results<br />
a road<br />
i. ,;ri";;;,'o'i<br />
contact, so that<br />
nur-rigg*<br />
vehiclcs can bc.o,npo.*,I in terms of<br />
tt'ci' 'csisra;';; ;;<br />
resu,i on,,,,ui',l;','''*;"".'J1tr#lijl<br />
[eJ' rn this il?ffilTi;; i$,-;Lffi*1::Trllfii.T'llJl?<br />
case,."!1,i.ri- *#;'r",ffi'rarerarry;;-; trigh ievers oil;::ilr.rl,TJrXtTff:]:htl<br />
slipperv surface ar specds i" rh*;;;;; of 30 mph.<br />
of morion<br />
broadsri
13th Internatlonal Technlcal Conference on Experlmental Setety Vehlcles<br />
Level<br />
0.6<br />
Figure 15. Comparison of the Range of Tire/Road Friction<br />
and Rollover Potentiales Evidenced by Side Pull Ratio<br />
lor 10 Roeds and 13 Vehicles<br />
contact for any severe maneuver on an arbitrary flat road<br />
should be viewed as indicative of a vehicle deficiency,<br />
and lack of contact is judged as proof of adequacy. This<br />
stratcgy is scriously flawcd bccausc ccrtain classcs of<br />
vehicles cannot pass such a test. In addition lo the<br />
problems with control of road friction and driver inputs,<br />
this simplistic approach ignores the lilrge population of<br />
cargo carriers and bus type vehicles that are unlikely to<br />
meet this standard when loaded to design intenl even<br />
though their "real world" performance is judged acceptable.<br />
When judged using the metrics of T/ZH, tilt tahle,<br />
or probably sidcpull, many of these vehicles will show<br />
Iess than half the resistance to rollovcr of sport utility<br />
vehicles.<br />
Summary<br />
<strong>The</strong> motor vehicle industry has had a long term<br />
interest in evaluating rollover resistance of its products.<br />
Whilc progrcss on rollover procedures has been limited,<br />
success has been realized in devcloping conscnsus tcst<br />
procedures for the more prevalent front and rcar collisions<br />
and for assessing the maneuver properties associated<br />
with braking, stecring and accclcration. <strong>The</strong> various<br />
candidate procedures for rollover resistancc tcsting<br />
reprcscnt compromises flmong the desires for face validity<br />
and cffcctivcncss yersus the practical considerations<br />
740<br />
of complcxity, rcpeatflbility, rcproducibility and resolution<br />
capability. In milny ways, compromise issues have<br />
bccn successfully resolved fur olhcr collisioh scenarios<br />
to the hencfit of both uscrs and manufacturcrs. <strong>The</strong><br />
compromisc proccss for rollovcr nccds further effort to<br />
meet both domcstic and inlcrnrtionrl needs. Meaningful<br />
progress in reducing rollover cvenls will require a better<br />
undcrslanding of the technical fucts and tradeoffs, plus<br />
a commitment to an otrjective treatrnent of the inllucnccs<br />
of the driver and environment ils well as the vehicle.<br />
Hopcfully, the discussion of thcse issues within this<br />
paper has contributcd to this proccss.<br />
References<br />
(l) Stonex, K. A. Roadside DtsiTin for Safety, Highway<br />
Research Board Proceedings, Volume 39,<br />
1960.<br />
(2) Sa/ety Programsfor Light'l'rucks and Sport Utility<br />
V e hi cl e s, I 990, U.S. Department of Transportation,<br />
Nalional Highway Traffic Sal'cty Administration.<br />
(3) Suzuki Submission to NHTSA. 1990.<br />
(4) Dilta Link. Inc.. Ro//ouer in Motor Vehicle Accidents,<br />
Final Draft Rcport, August 1988. An<br />
Investigation Conducted for the OIfice of Crash<br />
Avoidance Research. NHTSA.<br />
(5) Winklcr, C. and Campbcll, K. Centtr of Gravity<br />
Heighl: A Routul-Rttbin Measut'emeill Prttgrurn,<br />
Technical Report to <strong>The</strong> Motor Vchiclc Manufacturers<br />
Association, January, 199 I.<br />
(6) Riede, P.M, Cohb, W. A., and Leffcrt, R. L.,<br />
Typit:al Vehicle Paramelers J'or [)ynamit:s Sludies-<br />
Revlsdr/ for the /980's, SAE Preprint 840561,<br />
February, l9tl4.<br />
(7) Orlowski, K.R., Moffatt, E.A., Bundorf, R.T., and<br />
Holcomlr, M.P., 1{r'rrarrstrilction o.f Itollover Colli-<br />
.tir.,n.r, SAE Prcprint l{90tt-57, 1989.<br />
(8) Hiuwin, E. A. and Emery, L-,'l'he Crash Avttidance<br />
Rollttvtr Stutly: A Datahust: ftir the Investigation<br />
of Single Vehicle Rollover Crashes,<br />
National Highway Traffic Slfety Administration,<br />
Mav. 1989.<br />
(9) Cooperrider, N. K., Thomas, T. M., and Sclim, A.<br />
H., Testing antl Analysis of Vthicle Rollover<br />
Behavior, SAE Preprint 900366, February, 1990.<br />
(10) Chrstos, J. P., An Evaluutiott of Static Rollover<br />
Propensity Measurts, Nalional Highway Traffic<br />
Safcty Adninistration, May, 1991.<br />
(l l) Ebcrt, N. E., S'AE Tire Brttkittg Traction.Srrrvey.'A<br />
C o mp u ri so tt oJ' P u h I i t: I I i g hv, ay s a nd Te s t S urfa t: e s,<br />
SAE Prcprint 890638, Fctrrulry, 1989.
Section 3: Technica' Sess'ons<br />
s6.0.08<br />
<strong>The</strong> Urban Rollover: Characteristics, Injuries, Seat-Belts and Ejection<br />
G.M. Mackay, S. Parkin' A.P. Morris,<br />
R.N. Brown<br />
Accident Research Unit,<br />
University of Birmingham<br />
Abstract<br />
This paper prescnts an analysis of rollover crash<br />
characteristics and the injury consequcnces for occupants.<br />
158 rollover cases arc analyzed involving 282<br />
occupanls. Comparisons are made, whcrc appropriilte,<br />
bctwcen this study and previous studics conducted in thc<br />
1970's. <strong>The</strong> study found that generally, thc urban<br />
rollover is not a dramatic crash. Injury severity was<br />
found to be low to both restraincd and unrestraincd<br />
occupirnls, but ejectees wcre Inote likely to bc latally<br />
injured than non-ejectees. That however docs not imply<br />
a causal rclationship bctwccn ejection lnd the specific<br />
mechanism of injury. Roof crush was nol found to bc<br />
rcsponsible for injury causalion and thcrefore no<br />
rccomnrendations for changes in currcnt rool strength are<br />
madc. This samplc ntay under rcprcscnt high velocity<br />
crashes as the study was condttctcd in an urban cnvironmenl,<br />
a vicw supported by thc fact that only ZQVo of<br />
vehiclcs rolled more lhtn one revolution.<br />
Introduction<br />
A rollover accident, defined here as at least 90 degrees<br />
of vchicular rotitlion about any horizontal axis (uftcr<br />
Huclkc ct al. 1972 (l)) can on occltsion, bc onc of the<br />
more life threatening types of crashes. This is due to llrc<br />
unbcltcd occupant bcing exposed to high cncrgy, specific<br />
interior contacts or ejcction from thc vchicle which,<br />
Huelke et al, 1977 (2) claim, is consistenlly rnorc life<br />
threatening than containment. Sccondly, during such<br />
crashcs, the non-ejcctcd occupant is exposed to il grcllcr<br />
risk of serious injurics to the hcad, ncck and spine whcn<br />
the vehiclc is upside down due to thc rapidly changing<br />
nillure of several forcc vcctors applied ovcr a very short<br />
pcriod of time (Huclkc ct al, 1972.<br />
Previous studics have suggcslcd some consistcncy in<br />
the incidcncc of rollovcr accidcnts (in which injurics<br />
occur) in relation to thc gcncritl accident pilllcrn. Mlcklty<br />
and Tarnpen, 1970 (3) found that rollovcrs account for<br />
870 of such collisions in thc UK, while Mackay, lglJ I (a)<br />
rcviewing samplc studies in Europc showed thlt rollover<br />
accidents constituted 8-12% of all accidcnts. In addition,<br />
the Filtilt Accident Reporting Syslem, 1985 (5) shows<br />
thttt 9Vo of Americurt car crashes tre rollovers.<br />
Methodology<br />
This study exatnined 158 vehicles contain ing 282<br />
occupants involvcd in rollovcr accidents in and around<br />
thc West Midlnnds conurbation. All vehiclcs wsre<br />
examined rclrospectively and medical data wcre obtained<br />
from local hospitals. Additionally. thc occupanls<br />
themsclvos wcrc intervicwctl by qucslionltairc. Mackay<br />
et al, 198-5 (-5) give il morc cotrtprchensivc outline of thc<br />
mcthodology of this ongoing Occupant Injrrry Study.<br />
Act:idt:ttt Types<br />
Table I shows the numbcrs of vehiclcs involved in<br />
rollovcr events. Of thc accidents in which the numbcr of<br />
vehiclcs involved wus positively idcntificd, '73<br />
'5o/o<br />
involvcd only one vchiclc.<br />
Table 1. Number of Vehicles per Accident<br />
y'ehicles in<br />
rccident<br />
Huclkc ct al. 1972 (l) lound lhut irt u srtnple of 253<br />
rollovcr accidents, 79tk werc singlc vchiclc, lnd Mlckay<br />
and Tarnpcn, 1970 (3) found in lhcir sumplc tll' 89<br />
rollovcr itccidcnts, J}I/a wtrt:, singlc vchiclc,<br />
Occupant Agtt ttttd Sex<br />
<strong>The</strong> agc and scx ttistribution of the occupnnts is shown<br />
in Trhlc 2.<br />
Table 2. Age and Sex Distribution of the Occupants<br />
56l<br />
b<br />
0-10<br />
11-15<br />
16-20<br />
?1 -25<br />
26-30<br />
31-40<br />
41-50<br />
51+<br />
Total '<br />
Not known<br />
Total<br />
Number Percentage of<br />
Total (%)<br />
Percentage of<br />
knowns (7")<br />
Sinole vehicle 111 70.3 73.5<br />
Two+ vehicles 40 25.3 26.5<br />
Not known 7 4.4<br />
Total 158 100.0 1 00.0<br />
TO AL<br />
n<br />
a/o<br />
MALE<br />
FEMALE<br />
n l o / . n l o / o<br />
3 1.7 2 ?.9 c 2.0<br />
5 2.9 5 7.1 10 4.1<br />
54<br />
41<br />
?0<br />
23<br />
1 1<br />
18<br />
3 0.9<br />
23.4<br />
11.4<br />
1 3.1<br />
b-J<br />
1 0.3<br />
13<br />
18<br />
1 1<br />
I<br />
3<br />
s<br />
18.6<br />
25.7<br />
15.7<br />
1 2.9<br />
4.3<br />
1 ?.9<br />
b /<br />
C Y<br />
31<br />
32<br />
14<br />
27<br />
?7.3<br />
24.1<br />
12.7<br />
13.1<br />
5.7<br />
11.0<br />
175 100.0 70 100 245 100.0<br />
29<br />
204<br />
87 .g<br />
73.4<br />
4<br />
74<br />
1?.1 33<br />
278<br />
100.0<br />
100.0<br />
totel Includes known values<br />
(4 occupenls, sex not l(nown)<br />
13.4'/a ol thc occupiltlts wcrc tnalc, cotrtparcd with<br />
65.5t/a ntalc occuplrtcy l'or lll accidcnt lypcs (thc lattcr<br />
figurc taken front thc 0rtlirc Birminghant databasc, from<br />
which thc rollttvers wcrc sclccled for lhis study). Ol lhe<br />
sanrplc whcrc lhe lgc lnd scx is kntlwtr llt.8% ilrc ntlles<br />
in thc irgc range ltr-Z-5 (cotrrpitrcd with 18.770 l'or all<br />
accidcnt typcs). Clearly, nales in this agc range arc<br />
hcavily ovcr-rcprcscnlcd in rollovcr accidcnts, lhcrc<br />
bcing twicc a$ rlltny involvctl in rollovcrs tlran thc figurc<br />
for all accidcnl lypcs. If thc age rangc l(r-25. for hoth<br />
nrale and lctnllc. is onritlcd out of llrc tollls, rnalcs still<br />
conslilulc 7l.7Vo of tltc tolal rcntuining. showing lhal<br />
741<br />
# .<br />
ii<br />
'ij<br />
$<br />
'fl<br />
4<br />
rf<br />
;i<br />
-t<br />
i:<br />
re<br />
q<br />
.-s<br />
r.lR
1lth lnternailonel Technlcal conference on Experlmentat<br />
safety vehtctes<br />
malcs in general arc more often involved in rollover<br />
accidcnts. 34-BVo of the vchicles in the sample contained<br />
at lcast onc male in the agc range 16-2-5. On avcrage<br />
there were l.ll occupants per vehiclc in thc snmple. <strong>The</strong><br />
occupilncy for a vehiclc that had at leasf one malc in age<br />
rangc 16-25 rose to 2.5, lcaving the occupancy in lhe<br />
rcmaining vehicles at 1.4. Fcmales constituted 26.6Vo of<br />
thc whole sample, bul only 12.6F/o of the sample of occupflnts<br />
that were in vchiclcs that had at least onc mlle in<br />
thc flgc range l6-25, lcaving the female occupancy of the<br />
remaining vehicles at 39.\Vo.<br />
Restraint Use<br />
Table 3 shows rcstruint use for the occupirnts in the<br />
sample. Restraint usc for front seat occupants was<br />
89.97o, which is comparablc to observed national rcstraint<br />
use in general (variously observed at 8.5-9.57o in<br />
r 990).<br />
Table 3. Hestreint Use by $eatlng Position<br />
Seat position<br />
lestraint us6<br />
rHUN I<br />
n l %<br />
REAR<br />
l u "<br />
TOTAL<br />
n l v "<br />
iestfatned<br />
J nrestrained<br />
142<br />
16<br />
89.9<br />
'I<br />
0.1<br />
I 2.1<br />
Oe {<br />
143 6 9.4<br />
3 0.6<br />
Total 158 100.0 48 100 0 100.0<br />
Not known<br />
Total<br />
7'l 9 3.4 5 6.6<br />
81 .2 53 18I<br />
' This total includes known values only<br />
282<br />
100.0<br />
100.0<br />
Numher of Rolls<br />
Thc number of rolls experienced by the vehicles in the<br />
samplc is shown in Figure l, in quarter turns. <strong>The</strong>re<br />
were additionally 47 cascs in which the numbcr of rolls<br />
could not be eslablishcd, an inherent featurc of ir retrospective<br />
study. It was tlso not possible to establish how<br />
many of thc known sample had vaultcd, but Mtckay and<br />
Tampcn, 1970 (3) and Highr cr al, 1972 (7) borh showcd<br />
thflt this occurs in only about 57o of rollovers and it was<br />
therefore considcred thflt the results would not bc unduly<br />
affected. Figure I shows thilt after thc first quflrlcr turn.<br />
vehicles do not tcnd to stay on their sides, but topple<br />
ovcr onto either thc rool or whccls, this heing thc rnorc<br />
stablc condition. <strong>The</strong> majority, (63Vo), of the vehicles<br />
that rollcd over experienced a maximum of half a revolution.<br />
Thcrc is a very rapid, almost cxponcntitl, decrease<br />
in lhe numbcr of rolls. ln 20Vo of lhc known slrmple the<br />
vehiclc rolled more than I revolulion. 6% rolled more<br />
than 2 rcvolutions, and only 3% rollcd 3 revolutions or<br />
mote.<br />
In contrast Mackay and Tlmpen, 1970 (3) found that<br />
only 7% of their samplc rolled more than I rcvolution.<br />
This may partly bc duc to the change of dcsign of<br />
vehicles uscd in the UK in rhe past 20 ycars. Hight et al,<br />
1912 (1) found that 307o of their sanrple rollcd nore<br />
than I revolution, possibly illustrating the dil'fcrcncc<br />
botween Alnerican vchiclcs involved in mainly rural<br />
rollovers, versus UK vehicles involved in urban rollovers.<br />
<strong>The</strong> high level of restraint use in the current<br />
''10 o.75 'il;'..H';'T 2 2.28 z.so 2.7 ljj"<br />
Figure 1. Number of Rolls<br />
study, however, undoubtedly requires r more sevcre<br />
evont to occur in ordcr for a case to gct into the sarnplc.<br />
Finul Restittg Position<br />
Figure 2 shows the final resting positions of the<br />
vehicles in this study (Binninghanr l99l), and these<br />
results are conlpiu'ed to Mackly irnd Tanrpcn's, 1970 (3)<br />
carlicr Birminghrrn work, Highr et al, 1972 (7) rural US<br />
work, and Huelke et al, 1972 ( l) larger US sarrple.<br />
J<br />
F<br />
p<br />
{0"A<br />
z fll%<br />
=<br />
o<br />
z<br />
v<br />
L<br />
o<br />
ie<br />
20%<br />
g,,lg;;,,11;i_f;ll;1,,, Hll.i]im,., jl_t,, #<br />
WHEELS<br />
Figure 2. Final Re$ting Positions<br />
(Mackay and Tarnpen's rcsults include thc rollovers<br />
that cxpcrienced no more lhan I rcvolution, hcirrg g3?o<br />
of lhcir slrmple. Hight et al's rcsults include the rollovcrs<br />
lhat cxpcricnced no lnore lhtn 2 rcvolutions, bcing 94%<br />
of thcir sumple).<br />
Of the vehicles thal had I finul resting position on<br />
their sidcs tlrcrc were no difl'ercnccs between the rcsults<br />
found in this study, and Mackay and Tirmpen's earlicr<br />
work, both bcing at about u quarter of thc known sarnple.<br />
Both studics also found lhilt of the vehiclcs lhat had a<br />
final rcsting position on lhcir sidcs, lbout 3/4 cxpcrienced<br />
only l/4 of lr rcvolution. In conlrast, Hight et al's<br />
mainly rural US study found that 1/3 of thc vehicles had<br />
a final resting position on their sidc, of which only<br />
36.5Vo rollcd only l/4 of a revolution (half rhe frequcncy<br />
found in thc tsirminghilm studics). Huelke et al found in
their larger US sample that in only 16.5% of the known<br />
sample did the vehicle have a final resting position on<br />
the side. with no mcntion made of the number of turns.<br />
Impact Types<br />
Table 4 shows the types of accident in which the<br />
rollovers occurred. ln 27o/o of the known cases the<br />
vehicles suffered no, or no major impact before or after<br />
the rollover. This is very different to the results observed<br />
by Mackay and Tampen, 1970 (3) in which the figure<br />
was 5570.<br />
Trble 4. lmpac,tr Before and/or After Hollover<br />
Number of Percentage<br />
mDact tvDe<br />
v6hicles of knowns(o/")<br />
!one, or no major Purg 14 9.2<br />
mpact before or Tripped 13 8.5<br />
rfter rollover Otf-road 14 9.2<br />
Rollover after imoact NE 5s.6<br />
Rollover before imDact 1 ? 7.8<br />
moact bctore and after rollovet 1 E 9.8<br />
fotal l5 100<br />
lot known<br />
F<br />
In 65.4Vo of the known cases the vehicles did suffer a<br />
major impact previous to thc rollover (complrred with<br />
357o, Mackay and Tampen). <strong>The</strong>sc rcsults arc clcarly a<br />
feature of the urban environment.<br />
First Object Stuck<br />
Table 5 shows the first objects struck that initiated a<br />
rollover. 33.SVo of the vehicles suffered no major inrpact<br />
before the rollover. This is significantly less than<br />
Mackay and Tampen found (55.170). This study found<br />
that of the objects struck that initiatcd a rollovcr, 34.7Vo<br />
were other cars or light vans, and 6.lVo were heavy<br />
commercial vehicles. <strong>The</strong>se are considerably Iower<br />
frequencies than were found by Mackay and Tampen, the<br />
figures being 55Vo and l2.5Vo respectively. Mackay and<br />
Tampcn found that trces and posts represcnted22.SEo of<br />
thc primary impacts in thcir study, whereas the same<br />
objccts comprise 40.97o ol' the primary impacts in this<br />
study.<br />
Table 5. Flrrt ObFAr $truclr<br />
Number of Percentage of known<br />
Obiect struck<br />
vahinlac struck ohiectslT.)<br />
Other car or light van<br />
34<br />
34.7<br />
Heavy commercial vehlcle 6<br />
6.1<br />
Post<br />
27<br />
27.6<br />
Tree<br />
13<br />
13.3<br />
Other road furnlturo<br />
3<br />
3.1<br />
Wall or fence<br />
15<br />
1 5.3<br />
Not known<br />
7<br />
None, or no malor lmpact 53<br />
Total 158 100.1<br />
Of the 53 cases in which there was none, or no major<br />
impact before the rollover, about a third were pure rolls,<br />
a third were due to running off-road, and a third were<br />
due to some tripping mechanism. <strong>The</strong> curb represented<br />
over two thirds of the objects that tripped the vehicles.<br />
Section 3: Technical Sessions<br />
Door Performance<br />
Tablc 6 givcs details of door performance. In only<br />
37.3s/o of cases did all the doors function correctly, postcrash.<br />
At least one door jrmmed in 46.80/o of the<br />
vehicles, and at least one door opened in 15.87o of the<br />
vehicles. In no instances did rr door open and irnother<br />
become jammed. Door jamming miry bc a conccrrr whcn<br />
a vehiclc also incurs a firc. This problcnr did not occur<br />
in this study, with less lhan l7o of the rollover vchicles<br />
subscqucntly igniting (onc case).<br />
Table 6. Door PerformancE<br />
Door state<br />
Number of<br />
vehicles<br />
Percentage<br />
of total (%)<br />
Doors functlon colrectly<br />
Door(s) jamming<br />
59<br />
74<br />
37.3<br />
46.8<br />
Door(s) opening<br />
25 15.8<br />
Doors ooenino and iammino 0<br />
0<br />
Total 158 99.9<br />
Door opcning, in contrast, is of intcrest as thc chances<br />
of occupant cjcction arc exaccrbatcd as a result. <strong>The</strong><br />
injury conscquences of ejection are discusscd later in the<br />
papcr.<br />
W i nils c r e e n P t rfo r manc e<br />
<strong>The</strong>re are two gcneral methods for fixing windscreen<br />
into cars. Thc truditional mcthod is that of a ruhber<br />
gaskct bctwccn thc windscrccn apcrlure and the glass.<br />
Thc othcr techniquc is I'or thc windscrcen to be bonded,<br />
or glucd, directly to thc apcrturs. Of thc 158 vehicles in<br />
this study, 129 (8l.6Vo) hld a winclscreen fixcd with a<br />
gasket. <strong>The</strong> remainder,29 (18.4%) were bonded. Tablc<br />
7 and Figure 3 show the perforrnance of the two types r-rf<br />
fixing.<br />
Table 7. Wlndscreen Flxlng Performance<br />
State<br />
Fixino tvoe<br />
Sasket<br />
lord€d<br />
Total<br />
1/^<br />
u sore<br />
s<br />
E<br />
H 40%<br />
w<br />
r<br />
Fu lly<br />
intact<br />
26<br />
11<br />
37<br />
?3.4<br />
?0.2<br />
l;;::,,:,tl<br />
i;l;1 6 2. 0<br />
i:<br />
Part<br />
Rpnerel€ft<br />
?3<br />
12<br />
35<br />
22.?<br />
Fully<br />
canqrqlAr{<br />
80<br />
o<br />
86<br />
54.4<br />
,rffi<br />
37I<br />
i1i;:r',i:i;,;;i;<br />
GASKET BONDED<br />
FIXING TYPE<br />
Total<br />
o/"<br />
129 81.6<br />
29<br />
':'<br />
18.4<br />
100.0<br />
100.0<br />
Flgure 3. Windscreen Fixings Performance ;:<br />
743<br />
P *<br />
;E<br />
rl<br />
';<br />
:l<br />
.<br />
clE<br />
s j<br />
E<br />
i
llth ,ntemetlonel TechnlHAl Conterence on Experlmental Satety Vehlcles<br />
In over half of the rollovers the windscreen became<br />
fully separated from its fixing. In addition to this, 207a<br />
of the windscreen were made from toughened glass,<br />
which when brokcn also leaves a large aperture. <strong>The</strong>refore,<br />
in over 607o of the vehicles involved in this study<br />
there was a largc aperture in front of the front seat<br />
occupants, available for possible ejection.<br />
Seat Belts and Ejection<br />
<strong>The</strong> effectiveness of seat belts in all types of accidents<br />
has been well documented. Huelke et nl, 1977 (2) noted<br />
that belt usc reduced fatal and scrious injuries by 20-<br />
50Vo.<br />
Huelke et al, 1973 (8) found that 307o of non-restrained<br />
occupants were ejected during rollover collisions<br />
compared to 07o of restrained occupants. Of ejected lront<br />
scat occupants, 52Vo reccived critical to fatal (AIS 5-6)<br />
(AIS as dcfined by Marsh, 1972 (9)) injuries compared<br />
to 87o of non-ejected occupflnts. By comparison, Hight<br />
et Al, 1972 (7) found that 207o of unrestrained occupants<br />
were cjccted compared to 0.4Vo of restrained occupants.<br />
<strong>The</strong>ir study found that 52.2Vo of occupants received<br />
critical to fatal (MAIS 5-6+) (AIS as defincd by States,<br />
1969 (10)) as a rcsult of either total or partial ejection<br />
compared to ZVo of non-cjected occupants. However, iI<br />
docs not follow that thc specific ciluscs of the injuries<br />
were contiacts occurring outside thc vehicle. lt may wcll<br />
be that the process of ejection is an indicator of a seYere<br />
collision and the actual spccific mechanism of the injury<br />
may be a contact within thc vehicle prior lo cjection<br />
taking place. Both ejection and severe injury may be the<br />
outcome of a high energy rollover, they are not neccs'<br />
sarily related causally.<br />
Tables 8, 9 and l0 show the results of the current<br />
study. A significantly greatcr proportion oI unrcstrained<br />
occupants were cjccted either partly or totally from<br />
vehicles in rollover accidents (Xz = 77.61, P < 0.01). A<br />
significant number wcrc more likely to bc fatally injured<br />
than occupants who wcre contained within the vehicle<br />
(X2 - 55.59, P < 0.01). This finding is supported by data<br />
in table 10. Table l0 shows that 47Vo of occupants are<br />
likely to receive MAIS 5-6 injuries when thcy are ejected<br />
(wholly or partially) comparcd to 2.3Vo of contained<br />
occupilnts and again this is a slalistically significant<br />
relationship (X2 = 65.54, P < 0.01). This study compflres<br />
similarly with both the study by Hight ct al, 1972 (7) lnd<br />
Huelke et al, 1973 (8). Howcvcr, none of thesc studics,<br />
including the present onc, have a good inclcpcndcnt variable<br />
for assessing thc scverity of a rollovcr. Until such<br />
a parameter is available, and numbers of rolls, roll<br />
distance and roof deformation have all been proposcd,<br />
but have not proved to bc satisfactory, it is not possible<br />
to isolatc the specific part played by the ejection process.<br />
It is of interest that there were three cascs of rcstrained<br />
occupants being ejectcd.<br />
744<br />
Table L Hestralnts Versus Electlon<br />
Eiection Restrained Unrestrained Total<br />
\B<br />
NO<br />
3 (13.2)<br />
140 (129.8<br />
16 (s.B)<br />
47 (57.2\<br />
19<br />
187<br />
Total r43 63 206<br />
a2=27.61 With Yates' correction factor<br />
P < 0.01<br />
I * Restraint use not known has been ignored<br />
Numbers in parenthes€s represent expected values<br />
Table 9. Fatalities Versus EJection<br />
iection Fatal NonJatal Total<br />
YES 10 (1.4) e (17.6)<br />
NO<br />
1 1 (19.6) 2s2 (243.41 19<br />
263<br />
Iotal 21 261 282<br />
X2=55.59 With Yates' correction factor<br />
P < 0.01<br />
Numbers in Darentheses repre$ent exp€cted values<br />
Table 10. MAIS Score Versus Ejection<br />
Eiection<br />
YES<br />
NO<br />
MAts 0-4-<br />
10 (17.7)<br />
253 (241.5)<br />
MA|S 5-6.<br />
e (1 .o)<br />
6 (13.8)<br />
Total<br />
1 9<br />
259<br />
Total 263 15 282<br />
72 = 65.54 With Yates' Correction Factor<br />
P < 0.01<br />
-<br />
As defined by the Abbreviated Injury Scale, 1985 revision<br />
Numbers in parentheses represent expected values<br />
Head and Neck Iniuries, Resrraint.r and Eiection<br />
Tablc I I represents cotttbined head lnd ncck injury<br />
rates for restrained and unrestraincd ejectees and nonejectees.<br />
<strong>The</strong>rc is a significantly grcater chance of<br />
experiencing higher level head and ncck injuries (AIS 3-<br />
6) by unrcstrained ejectcd occupatrts complred lo nonejected<br />
restrained occupants (X'= 26.04, P < 0.02). It is<br />
of interest that the incidencc of AIS 3-6 iniuries to the<br />
head and neck for unrestrained unejcctcd occupant$ at<br />
lSVo is only slightly greater than for thc restrained<br />
unejected group at 107a.<br />
Teble 11. Head and Neck Al$ Versus Eiection and<br />
Restraint Use<br />
Eiection (restraint use) Ats 1-2 Ats 3-6 Tolal<br />
Ejected (unrestrain6d)<br />
5 (11.7 I (2.3) 14<br />
Non-6ject6d (unrestrained)<br />
Non-eiected (restrain6d)<br />
27 (25.9<br />
7I (73.4<br />
4 (5:1 )<br />
I (14.6<br />
? l<br />
88<br />
Total 111 22 133<br />
F:'ff,<br />
Numbers in paronlheses represent expected values<br />
Roof Crush<br />
Thcrc appears to be little to support the view that roof<br />
crush is directly rclated to occupilnt injury scverity in<br />
rollover accidcnts. Automotriles, espccially after rolling
more lhan one revolution, often sustain a certain amount<br />
of roof displaccment. Huclkc et al, 1972 (l), using dala<br />
from thc Highway Safety Research Insritute (HSRI)<br />
notetl a weak but consistent association between roof<br />
crush and injury severity as measured by the Abbrcviatcd<br />
Injury Scale (AIS as detincd by Marsh, 1972 (9)). <strong>The</strong>y<br />
suggested a strong associalion with injury when there<br />
was an extreme case of roof crush. i.e. in order of 25<br />
inchcs or more. However, the authors suggested that<br />
othcrwisc the relationship was more tenuous ("It is only<br />
when the roof is crushed downwards morc than two feet.<br />
thereby obliterating the compartmcnt spacc*found only<br />
in severe crashes-that the average injury level reachcs<br />
the'serious' category"). <strong>The</strong> authors concluded rhat<br />
other than suggcsting an association between roof crush<br />
and injury severity, rool crush is merely an indication of<br />
accident severity and that injury severity increases with<br />
accidcnt severity. Huelke's initial view was supportcd by<br />
a latcr study (Huelke and Compton, 1983 (l l)) which<br />
looked at rollover injuries in the Nationul Crash Sevcrity<br />
Study. <strong>The</strong>y found that only l1Vo of serious to lnaximuln<br />
(AIS 3-6) injuries in rollovers wcrc attributable to direct<br />
contilct with thc roof or olher structures at the top of thc<br />
car.<br />
Plastiras et al, 1985 (12) analyzed thc rclationship<br />
betwecn roof crush and injury risk. Thcy cxamincd<br />
twelve sub-compact cars of model years 1974-1978 and<br />
computed injury rates per 100 rollovers. <strong>The</strong>y found no<br />
significant linear correlation between crush and injury<br />
rate and thus concluded that --there<br />
is no apparcnt relationship<br />
between roof crush as measured by the roof<br />
crush test specified in FMVSS 216 and occupant protcction<br />
as measured by injury rates reportcd in the<br />
Wa.shington 51fl tc Accident Database."<br />
In our study, a comptrison was nradc bctwcen roof<br />
crush and MAIS. Occupants who had MAIS-O scores or<br />
whcrc the MAIS score was not known were excluded<br />
from this study as wcrc occupants in vehicles which did<br />
not suffer roof crush or where the roof crush was not<br />
known. Tatrle 12 gives thc results of the study. Thi$<br />
table was uscd to perform a Chi-square analysis (Table<br />
l3). From the available data, it would appca-r that roof<br />
intrusion and injury sevcrity arc not crusally rclated.<br />
Table 12. MAIS Versus Roof Intrusisn<br />
lntrusion(cm)<br />
1-5<br />
6-10<br />
11-15<br />
1 6-20<br />
21-25<br />
26-30<br />
31-35<br />
36-50<br />
50+<br />
I 2 3 4 5 6<br />
I<br />
12<br />
11<br />
5<br />
4<br />
3<br />
5<br />
1<br />
1<br />
I<br />
3<br />
4<br />
1<br />
1<br />
1<br />
0<br />
3<br />
0<br />
0<br />
2<br />
2<br />
3<br />
0<br />
0<br />
1<br />
1<br />
3<br />
1<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
1<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
0<br />
1<br />
0<br />
Sectlon 3: Technical Sessions<br />
Table 13. MAIS Versus Roof Intrusion<br />
Roof intrusion<br />
1 -1 5cm<br />
>15 cm<br />
MAIS 1-2<br />
4s (42.0)<br />
25 (28.0)<br />
MAIS 3-6 Total<br />
6 (e.0)<br />
I (6.0) 51<br />
34<br />
Total 70 15 85<br />
72 =2.36 With Yates' correction factor<br />
P is not significant<br />
Numbers in parentheses represent expected valuee<br />
Occupant lnjurits<br />
Table 14 givcs dctails of [J2 restrained drivers and<br />
thcir injuries. Only these occupants wcrc consitlcrcd in<br />
this scction in order thtlt il direct cornparison can be<br />
madc with the findings made by Mackay and Tampcn,<br />
1970 (3) which cxamincd predonrinantly unrcslrained<br />
occupants who wcre seatcd in the front.<br />
Table 14. Inlurles Hecelved by 82 Festrained Drivere<br />
Frd<br />
N€ck<br />
Ch6st<br />
Abdofrrefl<br />
Upper limbs<br />
Lower limbs<br />
Notable comgrarison$ ctn bc macie in Figure 4.96olt ol<br />
unrcslritincd drivers in the Mackty and Tampcn stutly<br />
suffercd hcad tnd facc injuries conrpared to 7B7o of<br />
reslrained drivcrs in thc currcnt study which suggcsts<br />
that rcstraints serve a purposc for preventing head<br />
contilcts with the steering whccl, roo[, 'B' pillar and side<br />
glass.<br />
Upper limbs<br />
LOWS r<br />
lifibs<br />
40% (36)<br />
89 unrostr5indd ddvdE 82 rEstrdinsd drivgrs<br />
Hed<br />
ano rac6<br />
96% (86)<br />
Necl t0% (s)<br />
Thorax<br />
24% l?1)<br />
Abdomen<br />
14% 1'12)<br />
'I 3<br />
4<br />
?<br />
0<br />
Upp6r limbs<br />
55% t45)<br />
LOW6f<br />
limbs<br />
43% (3s)<br />
HBad<br />
af,d taco<br />
78% 164\<br />
N*k 30"1 (2s)<br />
Thorax<br />
40% (33)<br />
Abdomsn<br />
12% (10)<br />
Mackay and Tampgn (1970) Mackay 6t al (lggt)<br />
Figure 4. Distribution ol Injuries<br />
Ncck injuries in thc current study were found to have<br />
incrcased from l0% to 30%. This could be explained by<br />
an incrcasc on soft lissue neck injuries.conrrnonly<br />
sustained lly corrcctly rcstraincd occupilnls lnd this view<br />
is supported by the fact that'72V0 o[ ncck injuries arc in<br />
the AIS- I catcgory. Both upper limtr and thoracic<br />
'72%<br />
injuries show lnoderalc increases. of thoracic and<br />
0<br />
0<br />
2<br />
0<br />
0<br />
0<br />
i:<br />
::<br />
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i!<br />
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1Ith lnternatlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
upper limb injuries are AIS-1. It is therefore suggested<br />
that the moderate, relativc incrcase in thoracic and upper<br />
limb injuries are explaincd by thc cffects of wearing seat<br />
bclts.<br />
, Table l5 gives dctails of all occupant injury scores<br />
regardless of both seating position and restraint use.<br />
<strong>The</strong>se scores arc rcprescnted in Figure 5. What is<br />
immcdiatcly clear from the table is thrt slight injuries<br />
(AIS l-2) arc far more likely to occur than serious to life<br />
threatening (AfS 3-6) injuries (85Vo-l5Va). Such data<br />
may suggest that rollovcr accidents ars not as potentially<br />
life threatening as has bccn prcviously thought. However,<br />
it is rcilcrated that accidents in this study are urhan<br />
in nature and therefore perhaps do not contain a more<br />
representative proportion of violcnt crashes of this typc.<br />
A follow up study could take this into considcration.<br />
Table 15. Occupant Inlury to All Occupants<br />
MAIS 2 3 4 5 6 Total<br />
Reqion<br />
Fled<br />
Neck<br />
OE<br />
51<br />
37<br />
I<br />
12<br />
3<br />
'|<br />
0<br />
4<br />
1 3<br />
153<br />
66<br />
Chest<br />
Abdomen<br />
41<br />
14<br />
10<br />
2<br />
10<br />
'I<br />
6 6<br />
7<br />
2<br />
0<br />
75<br />
27<br />
Upper limbs 95 28 6 0 0 0 12S<br />
Lower limhs 78 1 1 11 0 0 0 100<br />
Total 374 96 43 10 1 8 v 550<br />
Figure 5. Distribution of MAIS Scores<br />
Summary flnd Recommendations<br />
This paper presents analyses of rollover crash characteristics<br />
and injury consequcnces for occupants. From thc<br />
$tudy, the following conclusions can bc drawn:<br />
746<br />
MAIS 1<br />
. Males in the age-range l6-25 are over represented in<br />
thc sample used for this study.<br />
. Modcrn vehicles tend to roll one revolution or lcss<br />
in an urban cnvironment. <strong>The</strong> tnajority experience a<br />
maximum of half a revolution.<br />
. In known crsss,2TVa of vehicles suffered no major<br />
impact before or aftcr thc rolll in 65-4Vo of known<br />
cases, vehiclcs did suffer a major impact prior to<br />
rolling.<br />
. At least one door jammed in 46.Bs/o of vehicles and<br />
flt least one door opcncd in 15.8% of vehicles.<br />
. In over 607o of cascs, windscreen separation or<br />
breakage provided a possible forward e-iection route.<br />
. A significantly grcatcr proportion of unrestrained<br />
occupants werc cjcctcd (wholly or pirrtially) than<br />
corrcctly rcstrained occuplrnls. Ejcclccs are lltore<br />
likcly to be fatally injurcd tltan non-ejectees.<br />
' Unrcstrained ejectees are morc likcly to receive high<br />
lcvel head and ncck injuries than restrained nonejectees.<br />
Such injurics however may wcll occur prior<br />
to the ejection proccss. Non-ejected rcslraincd occupants<br />
are more likcly to sulfel lower levcl (AfS l-2)<br />
injuries than higher level (AIS 3-6) injuries.<br />
. Roof crush in this study did not rclalc to injury<br />
sevcrrly.<br />
. Restraint use mily scrvc a purpose for prcvcnling<br />
head contacts with steeritrg wheel, roof, B-Pillar and<br />
sicle ghss, but may result in rclativcly more minor<br />
injurics to upper lirntr and thoracic areas.<br />
, 85Vo of injuries in this study are AIS l-2 cornpitrcd<br />
to 150/o Als 3-6.<br />
In summary, the urban roll-ovcr is not a dramatic<br />
crash and overall injury severity is low to both rcstrained<br />
and unrestrained occuplnls. <strong>The</strong> use of seilt bclls is<br />
adviscd, but seat belts thcmselves iue not ncccssarily<br />
effectivc in the reduction of minor injuries and indccd<br />
injuries may bc sustained through their use.<br />
Roof crush is not a factor in determining injury<br />
sevcrity. Rather, injury scvcrity is an outcomc of<br />
accident severity and restraint use. This r;uggcsts that<br />
roof strcngth rcgulations are adequatc; indeed increased<br />
rool strength may raise thc centre of gravity of the<br />
vehicle, reduce visibility and effect a reduction in the<br />
absorption of crash cncrgy.<br />
It should be remenrbercd that the accidents in this<br />
study are urban in nfllurc and therefore violent rollover<br />
accidents muy be unrlcr-represented in thc sample. Future<br />
research should considcr rural data so thflt a comprehensive<br />
overvicw can be attained.<br />
Acknowledgements<br />
We are grateful to all members of the Co-operative<br />
Crash Injury Study and also acknowledge the hclp of thc<br />
spon$ors; the Transport and Road Research Lalroratory<br />
of the Department ol'Transport, Ford Motor Company,<br />
Rover Group and Nissan (UK) Limited.
References<br />
l. Huelke, D. F. et all ..Analysis<br />
of rollover factors and<br />
injury causation;" pp. 62-jg, proccedings of sixtccnth<br />
confercnce of the Anrgric:an Association tbr<br />
Automotive Medicine, 1972.<br />
2. Huelkc, D. F. et al; ..Injuries,<br />
restraints and vehicle<br />
factors in rollover car crashes;" pp. 93,10?, Accident<br />
Analysis and Prevcntion, Vol g,1977.<br />
3. Mackay, G. M. and I. D. Tampen;<br />
.,Field<br />
studics of<br />
rollover performance;" pp. 969-97.1, 1970 Inter_<br />
national automobile safety conference compendium.<br />
SAE paper 700417.<br />
Mackay, G. N. "Seat belts in Europe-their use and<br />
performance in colli.sions; "<br />
<strong>International</strong> symposium<br />
on occupant rcstraint, 1981.<br />
National Highway Traffic Safety Administration;<br />
'-Belt<br />
laws in I states in 1985 saverl 200 to 300<br />
livcs;" Fatal Accident Reporting System, t9g-5.<br />
Mackay, G. M. et al; "<strong>The</strong> merhodotogy of in-dcpth<br />
studics of car crashcs in Britain;" pp. 365-390, Fictd<br />
accidcnts, data collcction, analysis, methodologics,<br />
and car crash injury reconstructions. SAE Tcchnical<br />
Paper Series 8505_56, 1985.<br />
Hight, P. V. et al; "Injury 4.<br />
5.<br />
6.<br />
7.<br />
mechanisms in rollover<br />
collisions;" pp.204-227, Sixteenth Stapp Car Crash<br />
Confercnce, 1972. SAE paper 720966.<br />
s6-O-r0<br />
Study on Passenger Car Rollover Simulation<br />
Secilan g: Talhnlcel Sesslons<br />
Huelkc. H. F. et al; "Injury causation in rollover<br />
accidents:" pp. 87-l l-5. Proccsrtings of scventeenlh<br />
conference of the Alnerican Association for Auto_<br />
motive Mcdicine. 1973.<br />
Marsh, J. C. "Existing<br />
traffic irccident injury causa_<br />
tion data recording nrethods and the proltosal of an<br />
accidcnt injury classification schcme;" pp. 4,1,61.<br />
Proceedings of sixteenth conference of thc American<br />
Association for Automotive Mc
lgth lntemetlonal Technlcal Conlerence on Experlmental Safety Vehlcles<br />
its adjacent prcfcctures in Japan, using 1985 to 1989<br />
accident data of passcnger cars. One of the findings is<br />
that the percentagc of rollovcrs had relatively fcwcr<br />
occulrences than that of fronlal collisions'<br />
Collision Typc<br />
Frontal Collision<br />
Sidc Imprct<br />
Rear- end Collision<br />
Roll- over<br />
Complex<br />
(exccpt Roll-over)<br />
0thers<br />
Occupant Fatalities Perccnt<br />
(n=916)<br />
0 s 0<br />
Figure 1. Helative Distribution of Collision Type for<br />
Occupant Victims at the lbaragi Prefecture in Japan,<br />
1985 to 1989 Accident Data<br />
Figure 2 also dcscribes the relative distribution of<br />
collision types for occupant tatalities in the United<br />
Kingdom incidents, using t9tt3 to 191t6 accident data'<br />
This data shows that rollovers are few in cotnparison<br />
witn the total number of accidcnts, and the distribution<br />
is similar to that of JaPan.<br />
Occupant Fatalities Percent<br />
(n=1564)<br />
50<br />
%<br />
lm<br />
Figure 2. Relative Distribution of Collision Type for<br />
Occupant Victims in the United Kingdom, 1983 to 1986<br />
Accident Data<br />
<strong>The</strong> lJnrestrained Occupants to Eiectees<br />
<strong>The</strong> relative distribution of collision types for<br />
occupant non-ejection or ejection with unrestraints is<br />
illustratcd in Figure 3. As shown in this Figure' it is<br />
748<br />
Collision Typc<br />
Frontal Collision<br />
$idc Impact<br />
Rear- cnd Collision<br />
Roll-ovcr<br />
Complcx Accident<br />
(cxcept Roll- over)<br />
Otherc<br />
42<br />
#<br />
l sz<br />
found that the rilte of ejection for rollover is relativcly<br />
srcillcr than that of other traffic collision types.<br />
Collision Typc<br />
Frcntal Collision<br />
Side Impact<br />
Reer-end Collision<br />
Roll-ovrr' .<br />
Complcx Accident<br />
(cxcept Roll-over)<br />
Othcrs<br />
Non-cjection or Ejection Percentage<br />
%<br />
0<br />
50 100<br />
=l*<br />
29 fl non-cjection<br />
Figure 3. Felative Distribution of Cqllision Type lor<br />
Occupant Non-eiection or Ejection with Unre$tlaint'<br />
1985 to 1989 Accident Data<br />
E<br />
<strong>The</strong> relative contribution of injury severity (Abbrcviatcd<br />
Injury Scale; AIS) for non-ejection or ejection is<br />
shown in Figurc 4. This Figure illustrates thilt nonejectcd<br />
occupilnts with an AIS ovcr 4 arc itpt to be lcss,<br />
and ejccted occupirnls witlr tn AIS ovcr 3 urc rclatively<br />
larger. It is unclear whethcr a restraint systcm is<br />
available for reduclion of injury in rollovers, bul it is<br />
clear that thc usc of rcstraints is the primary prevention<br />
of ejection in rollovers. Huclke (l) concluded that for<br />
those occupants not ejected liorn the car' helts cl'fectively<br />
rcduce fatalities and lhe morc serious iniuries in<br />
rollovcrs.<br />
Non-ejection or Ejection Percentage<br />
To<br />
50 100<br />
Figure 4. Relative Di$tribution ol Injury Severity (AlS) for<br />
Non-ejection or Ejection with Unrestraint, 1985 to 1989<br />
Accident Data<br />
ffi<br />
ejection
<strong>The</strong> Occupants Injury to Non-Ejettion<br />
Figure 5 prcscnts the relarivc distribution of injury<br />
severity (AIS) for thc roof deformation in cascs of nonejection<br />
with unrestraint. It is sccn thilt occupants<br />
injuries are l'ew at AIS over 4 with non-cjcclion. Also,<br />
it is found that no signitictnt statistical relationship<br />
cxists bctween AIS and roof deformation for nonrcstrained<br />
occupants in rollovers.<br />
Roof Deformation Percentage<br />
AIS<br />
50<br />
%<br />
lm<br />
,t'l<br />
i+<br />
t<br />
,;1<br />
.H<br />
ffi<br />
@<br />
ffi<br />
smaller<br />
larger<br />
non-ctear<br />
Figure 5. Relative Distribution of Inlury Severity (AtS) tor<br />
the Roof Deformation in Cases ol Non-Ejection with No<br />
Restraint<br />
Huelke (2) indicated that for conrained occupants,<br />
those belted had fcwcr sevcrc injuries and fewcr fatalitics.<br />
Strother (3) found NCSS rollovcr/resrraincd data<br />
spflrsc, but noted that the cxisting data showed no<br />
rcstrained rollovers with an AIS 4. His studies results<br />
happened to be similar to ours. Huelke (4) obscrvcd that,<br />
even in thosc accidcnts where there was l3 to 24 inchcs<br />
of roof crash, the average injury to hp bcltcd occupilnrs<br />
was modcrate.<br />
Tablc I presents the compf,rison of injury severity to<br />
various parts ol-thc human body from aggressivc p;uts of<br />
vehicle body, without cjcction fronr the vchicles. <strong>The</strong><br />
rate of injury severity to the head is thc highcst of roral<br />
number of injuries. Also, the most aggrcssivc part of<br />
vehiclc is the roof when compared to othcr vchicle body<br />
pilrts, as illustrated in Table l.<br />
Ramp Rollover Tests<br />
'I'est<br />
Methodttlogy<br />
Various test procedures for passenger car roll-over lcsts<br />
have provided techniqucs and instrumcntltion for sludy<br />
and evaluation of vehicle structural effects. Also.<br />
occupirnt behavior resulting from rollovcrs produccd by<br />
the ramp test arc spccificd (-5). <strong>The</strong> rarnp proccdurc,<br />
which is reproducible between diffcrcnt lypcs of passengcr<br />
cars, provides rcalistic simulation,r^ of rollovcr<br />
accidents without collision.<br />
Seetlon 3: Technlcal Sesslons<br />
Tabl6 1. Relative Distribution of lnlury Severity to Various<br />
Parts ol the Human Body from Aggressive Parts of<br />
Vehicle Body<br />
(lm) (t00) (lm) (lm) (t00)<br />
<strong>The</strong> schematic ramp test ls shown in Figurc 6. As a<br />
severc turn usually will nol produce cnough of a rolling<br />
momenl lo causc the vehicle to rollovcr. lwo lechniqucs<br />
are proposcd. Onc is with thc rarnp locarcd so ils to lifl<br />
the front whccl which providcs thc rrccdcd rotling<br />
Inomcnt (5). <strong>The</strong> olhcr is with an adnptttion of control<br />
systcm of steering wheel. In thc first mcthod, thc rail<br />
curvfllurc ancl ramp hcight irrc dcsigncd to producc a<br />
rollover ilt a spccd ol'50krrr/h (see Figurc 6). Wirh rhc<br />
adaptalion. thc rollirrg monrcnl can bc prcciscly gcncratcd<br />
by quick nrorncnt of stccring whccl (scc Figurc 6).<br />
Figure 6. <strong>The</strong> Schematic Ramp Test<br />
. V:50&n',4I<br />
Pmition of opcniag<br />
the rt++fin8 whel<br />
Twelve ramp roll-ovcr tests were conducted using<br />
different typcs of Mitsuhishi Motors passcngsr ctrs trt a<br />
nominll spccd ol' 50km/h. Thcy wcrc a fronl cnginc,<br />
front whecl drivcr clrr wcighing approxirnutely l300kg,<br />
including an additional wcighl with a 2500ntm whecllxse<br />
taken ils a rough ilvcrilgc. For thcsc tcsts. lhc production<br />
cars ol lour-door scdlns, lwo-duor coupcs, und sporls-car<br />
typcs wcrc sclcclcd. In ordcr lo titkc a photugr-aph, hcad<br />
rctilrilinls on lhc lront and rc&r scats wcrc rsm()vcd. <strong>The</strong><br />
doors wcrc lclckcd and windows closcd prior to thc tcst.<br />
Thc slccring whccl was ilulomillicillly contrulllcd hy using<br />
an ;rccumulator urril on board. <strong>The</strong> crncrgency hrlkc was<br />
also on board. All tests are carried out on fltt concrclc<br />
in dry conditions.<br />
Ovcrall vehicle accelerations nre measured triaxially<br />
by accclcrornclcrs locatcd on lhc ccntcr pillars lt thcir<br />
intcrseclion with sidc sill.<br />
749<br />
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lSth lnternatlonal Technleal Conferenae on Experlmental Safety Vehicles<br />
<strong>The</strong> Hybrid III 50th percentile male dummies werc sct<br />
in thc lcft and right front in the seated position. Accelcromcters<br />
were placed in thcir head and ncck. Dummies<br />
were restrained wilh three point seat belts wi(h an<br />
inertiul lrtcking belt system. Also, a tension rclicver and<br />
load ccll wcrc located in line with the sect belt to<br />
mcasure the dynamic loads.<br />
Two on-board high speed cameras were equipped at<br />
the rcar position to document dummy movement. Offboard<br />
high speed camcras photographed the behavior of<br />
the vehicles. Onc high speed camera, to documcnt the<br />
overall vehicle movement, was locatcd at points on the<br />
right side of the test site.<br />
Ramp Roll-Over Test Resu/fs<br />
Vehicle Kinematics. <strong>The</strong> data from twelve ramp rollover<br />
tests results are shown in Figure 7, witlt regard to<br />
a number of rcvolutions of vehiclcs. When the vehicles<br />
just reach the position of operating the stccring wheel'<br />
thc stecring wheel is automatically controlled quickly to<br />
right dircction. <strong>The</strong> vehiclcs are driving leaning and<br />
rolled obliquely off thc ramp with the passcngcr side<br />
lcading at around -50km/h. First, the drivcr side of the<br />
root immediately contacted the ground, followcd by the<br />
pflsscngcr side. Typically, one revolution occurs in lhese<br />
tcsts. <strong>The</strong> differencc o[ vehicle type docs not clearly<br />
corrcspond to the number ol- rcvolutions.<br />
0.5 1.0 1.5<br />
rcvolutions of vehicles<br />
Figure 7. Number of Revolutions ol Vehicles<br />
Dummy Kinematics. <strong>The</strong> dummies movcmcnt is documcnted<br />
by using two on-board cameras. As thc dummies<br />
are nearly obligated on centrifugll force during lhe<br />
rollovers, dummies are almost tlways moved upward lnd<br />
outward to the extcnt permitted by the bclts. After<br />
contact is made with the roof, thc dumtnies heads remain<br />
adjacent to the roof or the roof rail. Oncc the driver<br />
dummy head is set, this orientllion is kcpt until the test<br />
is over. <strong>The</strong> passcnger dummy tends to lciltl to the driver<br />
dummy to the extent which thc belt can extend.<br />
750<br />
Dummy Measurenrcnts vs Vehit:lt: [)t:forrnutlon. <strong>The</strong><br />
head acceleration and ncck compression loads of the<br />
Hybrid III dummy are measured. <strong>The</strong> time-history of the<br />
roof delormation is obsLrrvcd by using a high speed<br />
camera attachcd to thc body slructure at the rear seat.<br />
From thcse fllcasurcrnents and otrscrvalions, the timehistory<br />
results for the neck comprcssion load and thc<br />
roof dclormation are schematicfllly shown in Figurc 13.<br />
According to thc observatiotts olltlined by using the hiSh<br />
speed camera, thc durnrny sitting on the side of the<br />
vehicle that approaches the ground first will contilct thc<br />
side glass due to the rotationll incrtia force. At this time,<br />
the neck compression lotcl contributes slightly to the<br />
component of lateral lotd. As thc vehicle rotation<br />
increascs, the dummy bccomcs invcrted and contacts the<br />
adjacent side roof rail and retnains there. Whcn thc<br />
dummy's hcitd stops, its torso keeps nroving towards its<br />
head stoppirtg al trtaxitnutn comprcssion. <strong>The</strong> maxllllufll<br />
neck loird is assumcd to occur at this timc. This is the<br />
reason for the high compression load in the neck. By<br />
observation from the high spccd catnera and confirmed<br />
by instrumented mcasurcnlcnts, tnost of lhe roof doformation<br />
occurs aftcr the peak neck loacl. According to<br />
Bahling, et al. (6) in the dolly rollover tcsl, thc<br />
maxinrurn neck load occurs bcfore the slructurul clcforrnation<br />
causss rrtaxitnutrt loltd.<br />
No. of vehicles X IOJ<br />
E".l<br />
t ':L<br />
2.6 3.0<br />
roof dcformation<br />
Time (sec)<br />
Figure 8. <strong>The</strong> Helationship Between the Neck Load, Roof<br />
Delormation and Time History<br />
L)untmy Injuries and ltoof Geonrctry. Here a factor<br />
affccting of the struclurll dclortnation on dummy injury<br />
is introtluccd. considerirrg l'icld accident investigations<br />
and rlnrp roll-over tests describcd above.<br />
Figurc 9 show the gcornctric roof height H defined as<br />
a factor. <strong>The</strong> roof height H' is assunted to lrc a peryendicular<br />
distance betwccn two parallel lines. <strong>The</strong> distrnce<br />
is a clearance bctwccn the line L conncctctl thc vcrtex<br />
point A o[ cngine hood with thc point B intcrsected the<br />
center-pillar, and the side roof rail in a sidc vicw, and<br />
thc linc L' parallel to thc linc L through the point C<br />
intersccted the front pillar and the side roof rail. By<br />
introducing flctor H, comptrison of roof deformltion on<br />
frctor H, we flrc ablc to understand clelrly, thc rollover<br />
phenomenon.
A: top of enginc hood<br />
B: intcrscction centcr pillar and<br />
sidc roof- rail<br />
Figure 9. <strong>The</strong> Geofletric Roof Height H<br />
Figure l0 shows the relation hetween roof deformation<br />
and roof height H. It is found that relations between the<br />
roof dcformation and roof height H seem to be linear.<br />
E<br />
.o 0.1<br />
o<br />
!<br />
E o.os<br />
D<br />
!<br />
o<br />
e<br />
Figure 10. <strong>The</strong> Relgtion Between Roof Deformation and<br />
Roof Height<br />
If a linear relationship exists between the roof deformation<br />
and the roof height H, the roof height H may<br />
relate to dummies injuries.<br />
Figurc I I illustrates the neck load versus the height H.<br />
Figure 12 prcsents HIC versus roof height H. As scen in<br />
thc Figures, that as H increases, the neck load and HIC<br />
tend to increase.<br />
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ii 05<br />
!<br />
c<br />
0 0.2 0.4<br />
roof height (m)<br />
Flgure 11. Thc Neck Loed Versus the Rool Height<br />
As the result of the introduced factor H, a possible<br />
relationship is identified between thc initial geornerric<br />
configuration of a vehicle and roof deformation or<br />
dummy injury.<br />
Sectlon i: Technlcal Sesslons<br />
0 0.2 0.4<br />
roof height (m)<br />
Figure 12. HIC Versus Roof Height<br />
Even in casc of higher roof height H, the vnlue of<br />
dummies HIC and neck load is lower lcvel relatively<br />
compared with a critcrion of injuries.<br />
Roof Height H and Roof Strenglft. Comparison of the<br />
static roof strength (FMVSS 216) for the roof dcfornration<br />
is investigated. As shown in Figure 13, therc is no<br />
stronger correlation than hetwccn the roof strength and<br />
the roof deformation. <strong>The</strong>refore, thc smtic roof strength<br />
is a wealcr relation to the dummy injury in the sense<br />
that it is stronger relation to the roof deforrnation. Here<br />
the static roof strength is given place to displacement X,<br />
defincd as the load, and satisficd with loads requircd in<br />
FMVSS 216 (see Figure l4).<br />
F<br />
E<br />
.e<br />
d<br />
E<br />
€ 0<br />
!t<br />
E<br />
0 0.0s o.r<br />
disphccment X rcachcd io load requircd<br />
FIYfVSS 216 (m)<br />
Figure 13. <strong>The</strong> Rool Deformation Versus the<br />
Displacement X<br />
Flgure 14. Static Roof Strength (FMVSS 216)
13th ,ntematlonel Technlcal Canference on Expeilmental Safety Vehleles<br />
fnverted Dummy Drop Test<br />
<strong>The</strong>re are, however, a few problems related to these<br />
methods with respect to thc repeatability due to the<br />
various type vehicles selcctcd. Among each test, initial<br />
conditions always have to decide, for the steering wheel<br />
to be operated quickly and timely. So only the invcrtcd<br />
dummy drop test is conducted in order to gain preciscly<br />
repeatable data.<br />
Drop Test Procedure<br />
<strong>The</strong> dummy is allowed to free fall from the inverted<br />
position, which is designed for each vehicle. In the area<br />
of dummy-to-ground, the part of roof cut off from the<br />
produclion vehicle is placed directly on the ground.<br />
Figure l5 dcscribes the schematic dummy drop test.<br />
Hybrid III dummy<br />
AM 5fth tile<br />
inner pad<br />
roof panel<br />
Figure 15. <strong>The</strong> Schematic Dummy Drop Test<br />
Drop Test,ltesults<br />
Drop test results with combinations of the drop height<br />
and dummy injury as shown in the insets of Figures l I<br />
and 12, are prcscnted in Figures 16 and 17. As the height<br />
of drop position increases, the dummy injury also<br />
increases accordingly. It is found that the tendency ofthe<br />
dummy injury in thc drop test corresponds to results of<br />
the ramp roll-ovcr tcst.<br />
btl<br />
l1<br />
x l0t<br />
1.0<br />
E €o 0.5<br />
.td<br />
o<br />
o<br />
g O<br />
0<br />
o Tcst data<br />
* Drop test<br />
0 0.2 0.4 (m)<br />
roof bcight or drop height<br />
Figure 16. Combinations of the Drop Height and ths Load<br />
of Dummy in the Insets ol Figure 11<br />
-o- Test data<br />
-*- Drop test<br />
{rn<br />
,/<br />
0 0.2 0.4 (m)<br />
roof height or drop height<br />
Figure 17. Combination of the Drop Height and HIC of<br />
Dummy in the Insets ol Figure 12<br />
Rollover Simulation<br />
Finite Element Method (FEM)<br />
For calculation of thc rollover phenomenon using<br />
FEM, it is necessary to solvc the motion equation with<br />
time integration. Explicit inlcgration is preferablo for<br />
solving crash sintulation problcns such as a frontal fixed<br />
barrier conrprrcd with implicil inlcgrillion, but implicit<br />
integration may be better than cxplicil in relatively<br />
longer behavior such as rollover. However, it is not yet<br />
cstahlished for culculttion. One program vectorizcd for<br />
the supercompulcr, is used to conduct the rollover simulation.<br />
FEM Model<br />
FEM modcl is explained as follows (7). Body panets<br />
such as thc frame, outer pancl, floor and roof are modificd<br />
with thin shell elcmcnts to calculate the impflct<br />
buckling modes. Suspcnsion unit and other chassis componcnts<br />
arc modeled as birr clcntcnls with the equivtlent<br />
stiffness. Flanges of pancls connected with spol wclding<br />
are modeled wilh each plate thickncss. Thc weight of<br />
components is attributed lo lumped lnass respectivcly.<br />
Rigid walls may be defincd providing external impact<br />
surfaces, whilc slide lines prevent pcnctratiort of internal<br />
structure surfaces during collision. Slide lincs arc availablc<br />
for framcs. Mesh olcmcnt sizing is 20ntm x 20tnm<br />
on an average considcring sound velocity. <strong>The</strong> numbcr of<br />
mesh elements is approximately 15000.<br />
Figurc 18 shows the FEM modcl for rollover simulation.<br />
Figure l9 illusl.rates the calculation rcsult.<br />
Figure 18. FEM Model
t'rli'rj<br />
Flgure 19. Deformation Mode<br />
Conclusions<br />
. In field accident investigations in Japan, rollover$<br />
are rclatively little, compared to other accidents. A<br />
highest severe injury rate to occupants not ejcctcd is<br />
to thc head.<br />
. <strong>The</strong> comparison of thc roof deformation or the roof<br />
hcight H on dummy injury in the improved ramp<br />
rollover tests is as [ollows:<br />
- Maximum neck load of dummy occurs before most<br />
structural deformation of the vehicle in ramp<br />
rollovcr test.<br />
- <strong>The</strong> relativc distribution of roof dcformirtion for<br />
neck loads is not stronger respcctivcly.<br />
- <strong>The</strong> roof dcformation and dummy injury are<br />
possibly relatcd to the roof heighr H, derivcd from<br />
the inirial geometric configuration of thc vehicle.<br />
. Thc rcsults of the invertcd dummy drop tcst is able<br />
to bc corresponded to the rarnp roll-over test.<br />
s6-o-11<br />
Roof Collapse and the Risk of SevereHead<br />
and Neck Injury<br />
Donald Friedman, Keith D. Friedman<br />
Liability Research<br />
Croup<br />
Abstract<br />
A survey of accident stltistics and harm to the head<br />
and neck from side impact and rollovcrs, suggest that<br />
vehicle upper structure should be the ncxt high priority<br />
goal in reducing scvcre casualties. Contrary to contentions<br />
thilt roof strenglh hus little inllucncc on lhcse<br />
injuries, thcsc rcsults from a multipliciry of studies,<br />
indicate that roof colllrpse should be eliminared, passive<br />
interior padding improved, laminated and retained glazing<br />
be installed and restraints improved by pretensioning<br />
rctractors. A stalistical analysis of the l9tt2 and 1983<br />
NASS filcs of rollover accidents, indicates a greatly<br />
increascd risk of severe injury to occupilnts undcr a<br />
collapsing roof section. <strong>The</strong> increascd risk was also<br />
demonstratcd by detailed investigation and analysis of l5<br />
rollover accidcnts using the protocol of SAE #890382<br />
(Live Subject Safety Rcscarch). <strong>The</strong> instrumented data<br />
from sixteen nearly identical, rollover tests conductcd by<br />
General Motors with conventional and rollcased roofs<br />
Sectlon 3: Technlcal Sesstons<br />
. By using the FEM, the rollover phcnomcnon is<br />
clarified in dctail.<br />
References<br />
l. Huelke, D. F., Lawson, T. E., Marsh, J. C., Injurics,<br />
Restraints and Vehicle Factors in Rollovcr Crr<br />
Crtshes, Accid. Anal. and Prev., Vol. 9, 1977.<br />
2. Huclke, D. F., Lawson. T. E.. Scorr. R.. and Marsh.<br />
J. C., <strong>The</strong> Effectivencss of Bclt Systcnrs in Frontal<br />
and Rollover Crashcs. SAE 770148. 1911.<br />
3. Strother, C. S., Smith, G. C.. James. M. 8.. and<br />
Warner, C. Y., Injury and Intrusion in Sidc lmpacts<br />
anrl Rollovers, SAE 1t40403. 1984.<br />
4. Huelke, D. F., Marsh, J. C., and Shcrman. H. W..<br />
Analysis of rollover Accidcnt Factors and Injury<br />
Causation, l6th Conference ol'thc American Association<br />
for Automotive Medicinc, 1972.<br />
5. SAE Handbook, J857, 1982.<br />
6. Bahling, C. S., Bundorf, R. T., and Kaspzyk, G. S.,<br />
Rollovcr tnd Drop Test-<strong>The</strong> Influcncc of Roof<br />
Strcngth on Injury Mechanics Using Belted<br />
Dummies, 34th Strlpp Car Crash Conferencc Procccdings,<br />
SAE 902314. I990.<br />
7. Sakurai, T., Aoki, T., On rhe Safery Body Strucrure<br />
of Finite Element Mcthod Analysis, l2th Intcrnational<br />
Technical Conl'crcnce on ESV, 89-2A-O-<br />
0r5, r989.<br />
and unrestrained and bclted Hybrid III dummics wcrc<br />
analyzcd and confirrncd thc incrcascd risk. Linriring thc<br />
deforlnation cxtcnt of vehicle roofs by lightweight<br />
structural chlngcs and simple und inexpcrrsivc force<br />
limiting, energy absorbing inrerior surlace modi[icalions,<br />
were dcmonslrated to rcduce thc risk of scvere injuries<br />
by a l'actor of at letst four. Furthcr rcductions can result<br />
from maintaining tlrc vchicle's directional stability by<br />
Anti-Lock Brlking Systcnrs. lirniling an occupilnt's<br />
contact velocity by cmergency tensioning rclrilclors on<br />
restraints and by rninimizing pilrtial ejection potcntial by<br />
laminated and rctaincd glazing.<br />
Introduction<br />
Automotive rollover irnpacts critically injure and kill<br />
thouslnds of pcoplc each yeu''u through head and ncck<br />
injuriesT''0 as shown in Figure L <strong>The</strong> tragic huntan<br />
consequences ofa quadriplcgia injury under an obviously<br />
collapsed roof naturally lclds to the prcsutnption thflt the<br />
rool' isn't strong cnough.<br />
<strong>The</strong>sc stutlics indicate that while the roof isn't strong<br />
enough, cxphining what happcned usunlly isn'l that<br />
153<br />
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1lth lnternatlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
simple and research agreement on the vchicle design<br />
features which cause rollover injurics has until now been<br />
masked by misrcpresentation.<br />
' z7er'o ol all HAHIV involvBs th6 HEad and N€ck<br />
* 41% of Head and N€ck HARM comss from contact with thd Foot,<br />
Root-BdgB, end A-Pillar.<br />
* 8% of HARM in Sids impacts is trom h6dd contectB with thB Bool AfBe.<br />
* 12,000 H6ad Injuri6s p6r y6ar of which 2000 are totally disabled and 5400<br />
have sevarB partial disability.<br />
* 310O Life threatening, but suruiving Spinal Cord Injuri6s.<br />
* 5900 Fatal Csruical Spins InJuries<br />
r 500 Quadripl€gics per y€ar<br />
Figure 1. Hsed and Neck Accident InJury Statlstlcs<br />
Perhaps because rollovers aren't publicly well understood<br />
and of lower priority, virtually no regulatory<br />
attention has been given to manufacturer's countermeasures<br />
for reducing or climinating the number of<br />
people annually killed and critically injurcd in rollover<br />
accidcnts.<br />
Moreover NHTSA secms to have given up on thc<br />
dynamic rollover tcst of paragraph S8.3 of FMVSS 20tt<br />
because in regulatory tcrms it isn't repeatablc cnough,<br />
although GM's l6 Malibu series tests illustrate useful<br />
repeatability. Instead there is now an NHTSA initiative<br />
on FMVSS 214 head injury testing, on FMVSS 2t6<br />
applicability to light trucks and vans and for an adjustcd<br />
static roof crush test as means of improving head impact<br />
protection.rr<br />
To address the issue of critical injury risk to occupants<br />
of vehiclcs in rollover impacts, analyscs of several data<br />
sources have been conducted. <strong>The</strong> analyses utilize data<br />
from:<br />
. Rollover Potential and Rate Studies,r2'r4<br />
. National Accident Sarnpling Systcm,s<br />
. Rollover Accident Case Studies,<br />
' Hcad and Neck Injury Data,rs-re<br />
. Rollover test data,zo'3r<br />
. Head contactsT'8 and padding studies32'33 and<br />
. Computer simulationss-r?.<br />
Thc rcsults of these analyscs provide insight into:<br />
. the vehicle characteristics that initilte ilnd cxacerbate<br />
thc injury potentifll of Rollovcr accidents;<br />
. the restraincd and unrestrained occupant kincmatics<br />
during the rollover cvcnt;<br />
. the injury mechanism of head and neck contact and,<br />
'the countermeasures which would mitigate the<br />
injuries.<br />
Background<br />
A rollover accident is usually the result ofan instability<br />
associated with the vehicle inadvertently lravcling<br />
with a velocity vector whose principal component is no<br />
longer in thc direction of the vchicles longitudinal axis.<br />
754<br />
Rollovcr propcnsity and the effect of Anti-Lock Braking<br />
Systems (ABS) to deal with directional stnbility during<br />
braking may be part of lhe solution.rr-rl<br />
Several studies have been conducted on behalf of<br />
vehiclc manufacturers suggesting that stronger roof<br />
structures are of little value in tcrms of occupant<br />
protection.25-30<br />
However, there is reason to question such conclusions.<br />
For example, some studies restrict thcmsclvcs to consideration<br />
of impacts in which thc ground contact and<br />
head impact point arc idcntical in space and/or time.<br />
<strong>The</strong>y conclude that stronger roof struclurcs are of no<br />
value in protecting occupirnts, and thcy imply that<br />
nothing can be done to reducc thc consequence of these<br />
impacts.<br />
<strong>The</strong>y do not consider the implicntions of stronger roof<br />
structures on vehiclc dynamics, windshield/glazing retention<br />
on roof strength and occupilnt ejection, or of<br />
stronger roofs to limit dcformation and collapse in the<br />
proxirnity of the occupant locfltion. Furthermore, they do<br />
not considcr the impliciltions of paddcd, energy absorbing,<br />
or shaped roof struclurcs, nor do they addrcss lhc<br />
issue of roof slructurc pcrfortnance on the risk of critical<br />
injury to occupants with head strikcs not flt the exact<br />
location of ground contact.<br />
Most currcnt production cilrs use less then .04" of<br />
stccl and l12" of ac()ustic dcadcning ntaterial to contilin<br />
and/or scparate an occupant's hcad from the ground; the<br />
increased window area of tempered sidc glazing facilitates<br />
ejections. Additionnlly, the roof support struclurcs<br />
allow the roof to collapse in a one foot drop tcst (much<br />
less a dynamic rollover event), ltnd thc occupant's head<br />
is exposed to numerous unpadded interior hurd points.<br />
In short, many prcvious studies do nol considcr the<br />
implications of currcnt roof structure dcsign on thc risk<br />
of critical injury, nor what can bc done wilh available<br />
countermeasurcs. <strong>The</strong>refore, the two primary purposes of<br />
this papcr are to: define the ftctors on which Head and<br />
Neck Injury Risk depends; tnd to idcntify safety features<br />
which could rcduce the frequcncy and severity of such<br />
injuries pilrliculflrly in rollover accidcnts.<br />
Propensity to Rollover and Rollover Rntes<br />
Per 100 Fatalities<br />
Collision Avoidttnce. An NHTSA and a confidential<br />
sturlyr3 has dcrived estilniltos of field rollover rates for<br />
cars and other light vchiclcst detertnined the extcni to<br />
which these rollover ratcs arc influenced by half the<br />
track width divided by thc ccnter of grrvity elevation<br />
(T/2H), aftcr control for other vehiculiu factors itnd<br />
normalization to cotnmon expo$urc conditions; and has<br />
characterizcd thc rollover rates by injury severity; atnong<br />
other comparativc evaluatiotts.<br />
Light trucks, vans and utility vehicles experience<br />
much higher (1.5 to 2 times) overturning rates thtn<br />
automobilcs.5 Our experience and invcstigations indicate<br />
thilt these vchiclcs arc l'requently used as passcngcr car$
with lightly loaded rear wheels. When so londed, an<br />
emergency stccring maneuver accompanied by braking<br />
tends to lock up the rear wheels rcsulting in a loss of<br />
directional control, laterill skidding and rollover.<br />
Shortcr whcelbases also result in higher yaw rates and<br />
indicate vchiclcs with a lower yaw moment of inertia<br />
which combine to produce lateral skidding and potential<br />
for roll. Thc use of Anti-Lock Braking Systems (ABS)<br />
on such vehiclcs may be a most important everyday safety<br />
feature on lightly loaded pickups, vans and utility<br />
vehicles with as much or morc safety benefits than other<br />
crashworthiness improvements. Running-off-thc-road is<br />
usually the first event in a rollovcr of any vchicle and<br />
ABS could signiticantly reduce the frequency of such<br />
occurrences.<br />
Crashworthin ess. As in most studies of those types, an<br />
inherent assumption is that equal protcction is provided<br />
for the occupants and no attempt is madc to correlate the<br />
fatality or sevcrc injury ratcs with intrusion or restrilint<br />
features nor to flsse$s the likelihood of reducing the rates<br />
with practical modifications.<br />
<strong>The</strong> resulting claim is that vchiclcs which overturn<br />
more frequently are less safe than ones which do not and<br />
should be taken off the miuket. Manulacturers who have<br />
a duty to providc comparable statc-of-the-art protection<br />
can do so either with collision flvoidance features or with<br />
occupanl protection fcatures such as stronger roofs, roll<br />
bars, emcrgency tensioning retractors, passive interiors,<br />
laminatcd glazing, etc. or preferably all.<br />
As addressed in a previous studyr8 dealing with frontal<br />
impacts, thcre is no doubt that as designed and inherently<br />
(by the laws of physics)<br />
"small cars flrc lcss safc than<br />
large cars," but by attention to occupant protection and<br />
restraint design, the disparity can be substantially<br />
ameliorated. As air bags are installed in all vchiclcs<br />
(probably by 1994) and as increased CAFE forccs large<br />
cars to lighten, their compatibility and the disparity will<br />
improvete although some intrusion in small cars may<br />
remain. When that happens, the frcqucncy of occuncncc<br />
of scvcre to fatfll injury in frontrl rccidents will reach a<br />
lowcr limit as a result of vehicle factors und the residual<br />
will bc more occupant rclated and morc independent of<br />
size.<br />
<strong>The</strong> same situation applies to side impact and rollover<br />
accidcnts, using the same specific amelioration techniques<br />
of rcduccd intrusion, improvcd passivc interiors,<br />
and automatic tensioning of belts.<br />
National Accident Data Analysis<br />
A study of rollover impactsoo was conducted in 1986/<br />
1987 using data from the 1982 and 1983 National Accident<br />
Sampling System. Rollover cases involving hardtop<br />
automobiles with known data for variables of interest<br />
were considered.<br />
A review of the actual hardcopy data aided in identifying<br />
rollover types and the nature of damage associated<br />
with thc occurrence of injury. <strong>The</strong> rcsults suggcstcd that<br />
Sectlon 3: Technlcal Sesslons<br />
roof damage dcscriptions rctative to occupant locations<br />
would correlate with critical injury occurrcncc.<br />
It was also notcd that ejection and cjection paths may<br />
also he related to rool crush and dislortion or may bc a<br />
secondary cffcct rclalivc to thc roof crush. <strong>The</strong> hardcopy<br />
data study suggcstcd tlrc following;<br />
. Cases with significant roof crush at the occupant<br />
location or expected contact area appear to gencrally<br />
result in substantial injury;<br />
. Cascs with substantial othsr darnage nray distort data<br />
analysis rcsults (e.g. frontitl or side impacts in which<br />
there was also a rollovcr); and,<br />
. Ejcction and ejcction pilths mry also be related to<br />
roof crush and distortion or may bc a secondary<br />
effect rclrtivc to thc roof crush.<br />
As a result of the hardcopy data study, the computerized<br />
data were ulilized to chiuaclerize the proximity of<br />
roofcrush to occupilnl locltion, and cases were excluded<br />
from data study in which non-top darnagc cxlcnt was<br />
greater than 3 as were those occupants totally cjccted<br />
through the door arca. Thc dctlils of thc rccoding and<br />
mcthodology rre contrined in Appendix A.<br />
<strong>The</strong> Statistical Analysis System was lhcn used to study<br />
thc cornputcrizcd dltir. Thc results show a dramltic<br />
difference in the risk of critical injury or death whcn the<br />
darnage in the proxirnity of thc occuptnt cxcccds a<br />
damage extent of 3. Spccil'icnlly, thc incrcascd risk in<br />
rollover impacts for occupants in the proximity of<br />
signiflicant roof crush is approxirnately 4 to I.<br />
Table 1. Analysls Hesults Showing Comparison of Risk<br />
for Occupants not in the Proximity of Significant Floof<br />
Crush in Rollover lmpacts<br />
Raw tlatr fElght.d RsEuItE RlEk<br />
of<br />
AIS AIS AIS ATS ATS<br />
crtegory 0-3 4-6 o-3 4-6 4, 5, 6<br />
Proxinal Dilage o-l 307 5 58541 2Zg ,0039<br />
Proxinal Dahaqe >3 138 5 15170 ?43 .ots8<br />
<strong>The</strong> tabular results are shown in Table I and show a<br />
factor of 4 increase in the risk of clilicul injury or dcath<br />
in rollover inlpacts when th0 occupant locittion is in thc<br />
proximity of significant roof crush cornpared with<br />
occupants who are not.<br />
Rollover Case Studies<br />
Fifteen cases of critical injury or fatality have been<br />
invcstigatcd, rnost hut not all on an in-dcpth basis. Thcse<br />
real world rollover cases describcd in Table 2, were<br />
analyzcd by compulcr sinrulatiort lo charactcriz.c lhe<br />
accident, the occuplnt kinernalics and lhe injury mechanism.<br />
In each case altcrnative means to reduce the level of<br />
injury were considered rnd then demonstralccl to be<br />
fcasiblc within practicality and economic constraints.<br />
<strong>The</strong> mitigation rneans considered were fl strongcr roof,<br />
a shaped roof (like cars of the 50's and the Minicars<br />
/)f
lSth lnternatlonal Technlcal Conference on Experlmental Satety Vehlcles<br />
Teble 2. Hollover Accident Case File Summaries<br />
Case Vehlcle<br />
1. 1975 Finto r 5<br />
?. 1983 Blazer<br />
3. 1986 EEsort<br />
> 3<br />
: 5<br />
4.<br />
5.<br />
1981 Lesabre<br />
1984 Toy p/U<br />
> 3<br />
> 4<br />
6. 1980 280 Z<br />
?. 19?6 Dodgs<br />
8. L983 Canaro<br />
> 2<br />
r 5<br />
E 5<br />
9, 1981 F150 P/U<br />
IO.1988 25OO P/U<br />
11,1985 Bronca<br />
12.1984 BUW<br />
> 2<br />
= 5<br />
= 4<br />
= I<br />
13.L981 Subaru<br />
14.1988 Sahuraa<br />
* I<br />
= O<br />
15.19762602 -3<br />
ICS/ 5<br />
rBD/ 6<br />
zCS/ 5<br />
1C5/ 5<br />
LCS/ 4<br />
lBD/ 4<br />
zCS/ 5<br />
r.csl 5<br />
lBD/ 5<br />
lcs/ 5<br />
rcs/ 5<br />
zBD/ 6<br />
lCS /5<br />
LCS /5<br />
subtotal I veh w/Rc >3 10 Inj >4 u/Rc, I Inj
Secfion 3: Technlca, Sessjons<br />
in the same vehicles seated where there was no with the earth) injury meflsures rt thc AIS = J<br />
significant rooI dclormation.<br />
quadriplegic lcvcl.<br />
. Receiving an aligncd neck comprcssion load of more When we substitutcd a {rt)Ot) pound stitf 2l(X) ft-pound<br />
than 4000 n (interpreted frorn Biomechanical Rc- roof, deformillion was linritcrl to ubout l5 cm, thc ncck<br />
search Criteria and applicd to the Hybrid III comprcssion was atrout 2300 ncwtons (a muclr lower<br />
simulations) oftcn in conjunction with a moment probability o[ pcrnrancrrt debility). Whcn we addcd trclt<br />
torquc or shear force. This is projected to result in emcrgcncy tensioning rclrflctors,o5-o* of thc trclt wind-up<br />
some form of compression fracture and subluxation. lype patcnted in the 1970's, lo this altcrnative roof<br />
Fourlccn of the victims bccame quadriplegic from con[iguration the neck comprcssive lotd droppcd to l06l<br />
crushing of the cervical vcrtcbrae (1,3,4,5,7,8,10, n. A paranetric analysis was also conductcd for a rangc<br />
I I,15) with roof collapse (extcnt Brcatcr than 3) ovcr<br />
their seating position while all thirteen other occupants<br />
o[ the same vehicles not undcr collapsed roof<br />
of stiffer earth surlhces with a similar range of rcsulls.<br />
Analysis of GM Rollr-rver Test Data<br />
sections rcccived minor to moderatc injuries.<br />
Rollover crash tcst data availablc l'ront Gcneral Motors<br />
. <strong>The</strong> above injuries were sometimcs in comhination were review*4.15-16 CM nradc no allcrnpt to rnilke lhcsc<br />
with shcar forces and momcnt (torque) loads on thc tests represcntative oI the rcal world. <strong>The</strong>reforc. curcful<br />
head and ncck rcsulting in postcrior or antcrior analysis and judgement nrust bc applicd whcn contparing<br />
cervical fracture and displacement.<br />
these injury mcnsurc rcsults with thc hurnln injury<br />
rcsults of accidsnt :itatistics and casc invcsiigltions.<br />
A Sample Case study involving Roof Crush<br />
Clrc nrust bc takcn lo propcrly intcrprct tcsts with<br />
This 65 mph loss of control, running-off-the-road dunrrnies. who cun ncithcr huld on. britcc thcnrsclvcs.<br />
acciclcnt resulted in a 20 mph 360 dcgrce roll on dirt in protcct their hcad and ncck with the arms, nor kccp thcir<br />
a vehicle wilh a secondary supplier's undevclopcd Targa<br />
(substantially weakened) roof which collapsed (at about<br />
chin on thcir chcst. In l;rct, dummics rrc dcsigncd to bc<br />
-'in<br />
position" with ils held erect and ncck aligned for an<br />
3300 pounds and 2300 ft-lbs) to thc window sill on I axial conrprcssion lord llrrough thc lop of thc hcad. And<br />
rcstraincd woman with more than fivc inche.s of normally whilc a person nright drop thcir head itftcr a first impacl,<br />
seated head clearancc. Thc injury was il ssvsrc cxlcnsion the dunrnry rcsets itself for mlny inrpacts in the coursc<br />
comprcssion of the cervical spine with postcrior lractures of a roll.<br />
of C-2 as well as symmetrical posterior hurst l'rilcturcs at<br />
c-6.<br />
Thc GM rollover te$ts are right roll dolly hunch tests.<br />
In the first scric.s ol'll tcsls thc drivcr and right frrrnt<br />
<strong>The</strong> vehicle trajectory was simulatcd in 3-D from hkc- passenger dumrrtics wcrc unreslraincd, whilc in thc<br />
off and touchdown marks in the soft earth. the roof crash second set of 8. lhc durnrnies wcrc rcstrlitred hut with r<br />
pulse and dcformation were modelcd from FMVSS 216 bclt which wirs signilicantly slackened ler rcprcsent how<br />
and compuler dcrived stiffness estimatcs. <strong>The</strong> occupant hurnan occupilnts wcilr lhcrn and allow 4" ol- vcrlical<br />
kinematics and injury mechanism compulcr simulations motion at I g.<br />
resulted in the injury mcasures of Table 3.<br />
Thc tcsts were conductcd with a vehiclc inilirl roll<br />
position 23 dcgrees to thc horizontal and launclrcd l'rorrr<br />
Table 3. Retulting Inlury Measures from Actual and ahout 9 to l2 inches abovc tlrc ground with a spccd of<br />
Alternative $imulations ol Example Rollover<br />
approximrtely 5l Kilonrctcrs ['cr Hour (KPH). That<br />
Paraneter Actual stlflcr<br />
Eoof<br />
stlffsr Roof<br />
pretenBlonlng<br />
&<br />
nrcans thc lirunch pruduccs a clockwisc roll (looking<br />
ll'orn thc rcar) and thilt thc drivcr dunrnry cxpcricrrccs a<br />
Crueh over victim<br />
BeIt Slack (each)<br />
TorEo belt loncl (n)<br />
Lap BeIt load (n)<br />
HIC<br />
Neck Shear FordeB<br />
HeqlC MOFent<br />
Feak Nsck ConpreEsivs Forcs<br />
30ffi<br />
r.75fl<br />
0<br />
4o5 n<br />
343<br />
-95 n<br />
? nn<br />
4727<br />
lscn<br />
r.7sil<br />
0<br />
I3o3 n<br />
67<br />
l7B n<br />
f.5 nh<br />
2309<br />
15cm<br />
lO95 n<br />
2607 n<br />
26<br />
A45 n<br />
-31 nfr<br />
1061<br />
signil'iclnt forcc to rllovc, aclr.rillly nroving upward and<br />
lo its riglrt rt luunch.<br />
Thcse lcsls with 1983 Chgvrolct Mulihu l-our door<br />
vchiclcs arc rnost likcly lo producc l first roof to ground<br />
contilct on lhc drivers sidc roof (thc far sids in this<br />
casc), rnd are lnost likcly to coll;rpsc therc first (wilh<br />
$tflndard roofs) antl produce a drivcr-injury.<br />
<strong>The</strong> analysis indicated that the roof was collapsing at Half the vchiclcs in ctch series wcrc llso modified to<br />
about 15 feeVsecond at about 200 dcgrccs of roll in includc an unpaddcd 160# roll clgc. Nonc of the roll-<br />
alignmcnt with her cervical oricntltiun ilt contflct with cagcd vchiclcs dcforncd. rnd lwo of the cight stlndrrd<br />
her head somewhat in extensiorr duc to il concurrcnt vehiclcs did not collirpsc. This suggcsts that l ntuch<br />
violcnt vchicle yaw lnotion- Sho was oll'the scut, rnoving more rnodcst wcight incrcase for roof support struclurc<br />
lowards the roof with about an eight fool/second vcloci- would bc sufficienl to uchicvc tlrc benefits of the<br />
ty, which was in the process of bcing arrcsted hy the rollcaged vchiclcs in rcducod injurics.<br />
belts with 1.75" of slack on each side. Thc contact In thc cight unrestririncd CM tcsts there were inside<br />
produccd dummy neck compression (from head contact thc car, 43 Potcntitlly Injuriou.s Ilnpuc:ls (l)ll) = or >2000<br />
t\t
13th lnternatlonel rechnlcal conlerence on Expertmentat safety vehtctes<br />
newtons-the GM presumed thrcshold of any axial compression<br />
injury for an averagc of 3.5 such impacts pcr<br />
lcsl for thc far side drivpr, whilc @ 4000 ncwtorrs (rhe<br />
GM scrious injury probability measurc) or morc thcre iue<br />
less than 2 per test. For the nearsirle passengcr, there arc<br />
only about 1.5 PII per tcst and only two total interior<br />
contacls above 4000 n.<br />
In thc eight rcstrained tests inside thc car, therc were<br />
a similar 39 PII's but there werc 5 pilssenBcr contacts<br />
above 4000 n; estimated dummy contact vclocities wcre<br />
.83 to 3.3 m/s.<br />
As cxplained in Figure 2, Biomechanical researchers<br />
suggest using 4000 newtons of short dura(ion axial<br />
compression (Metric l) for relating neck injury measures<br />
to the onsct of severe neck injury probability. <strong>The</strong>y also<br />
rclate neck momcnts excecding 190 nm in flexion and 57<br />
nm in extension (Metric 2) to critical injury.<br />
Table +. Results of GM Test Data Showing the Fraction of<br />
Cases Exceeding Neck and Moment Criterion (Metric 1)<br />
FoBj.t.lon RestEaint<br />
:::I_If:<br />
Relative<br />
!:_i:]l_<br />
condition<br />
Ilnrcstrained Restratned<br />
st-andard<br />
Roll cage<br />
Far<br />
Far<br />
side<br />
eidB<br />
4/4<br />
4/4<br />
4/A<br />
Z/4<br />
B/B<br />
6/E<br />
Standard Nearside 2/4 t/4 3/B<br />
RoIl cage NearEide 2/4 3/4 S/B<br />
For the Hybrid III dummy injury measure rcsults ro<br />
corrcspond to thc certainty ol' a reirl world critical neck<br />
injury uccurring, we assunrcd that axial compression<br />
grcater than 5000 newtons accompanied by 1000 newtons<br />
of shear (Metric 3) would be appropriate.<br />
Table 5. Results of GMTest Data Showing the Fraction of<br />
Casee Exceeding Neck Moment Criterion (Metric 2)<br />
Foaltl6h<br />
ReIatIv6<br />
T:I:r: ::_T11_<br />
stanalard<br />
ROII cagr<br />
FEr<br />
Far<br />
EIde<br />
sLde<br />
z/4<br />
2/4<br />
R6Bt"aInt<br />
condltlon<br />
rotal<br />
z/4 4/8<br />
o/4 z/a<br />
Standard Nearsld. O/4 D/4 o/a<br />
Roll cage Nearglde r/4 O/1 L,/B<br />
Thus, three metrics have bcen identified for interpreting<br />
the data from the Hybrid III durnmy, two of which<br />
(Metrics I and 2) are intcrpreted (Tablcs 4 and 5) as<br />
corrcsponding to prcdicting the onsct of severe ncck<br />
injury probability whilc the third (Mctric 3) relrresents a<br />
mcdian probability of critical neck injury (such as might<br />
hc appropriate for modeling a known, having-actualtyoccuncd<br />
critical injury) shown in Tablc 6.<br />
Thcse metrics werc evaluated using the drta availahlc;<br />
the results from each test arc prcsented in Appcndix B,<br />
whilc the results arc summarized below.<br />
Of these rcsults perhaps the most notablc is the<br />
dramatic diffcrcncc in the results for the far sidc metric<br />
3 between standard and roll caged vehicles. As can be<br />
seen in Table 6, lhere were ,l(, cases in which a far side<br />
7s8<br />
occupflnt in the roll caged Malibu ever cxceeded the<br />
Metric 3 criterion, while a// of the far side rsstrained<br />
occupants in the slrrnrlarrl Malibu exceedcd the lirnit.<br />
And thc rocrfs of lhc standard vehiclcs whose occupilnts<br />
did not excecd the melric, did not collapse.<br />
Table 6. Hesults of GM Crash Test Deta Showing the<br />
Fraction of Cases Exceeding the 5000 n Axial Neck<br />
Compression and 1000 n Shear Force Criterion (Metric 3)<br />
FoBleion ReBtralnt<br />
Ralatlve condltion<br />
Roaf Type to RoIl Unrestrained Restrrlnod<br />
Standard Far side Z/4 4./4 6/E<br />
Roll cage Far side o/4 O7o ola<br />
Standard Noar6lde L/4 O,/4 LlA<br />
RaII cage Nearside O/4 Z7n z/a<br />
Thcrc are a nurnbcr of othcr interior injury mcasure<br />
results which iue ol' interest. For exanrplc there wcre<br />
only 2 cilses of HIC grcater than 1250, I in standard roof<br />
and I in roll cagc vchicles. Thcrc werc lwo cases of<br />
partial flnd one total cjection.<br />
Unfortunilrely, CM did not publish photographic<br />
derivcd data such as when, whcre lnd how much thc roof<br />
crushcd as a function of tirne. Thcre werc only thrcc<br />
plots of neck compression lorce vs time for PII 2L3, 3L4<br />
and 7L4 on which roof contact was displlycd at the<br />
bcginning of the neck conrpression and indicated lhilt<br />
roof crush occurred latcr. <strong>The</strong> electronic data from 4<br />
vertical accclerometcrs indicated thal contacl occurred<br />
some 25 to one hundrcd rrrilliseconds elrlier as shown in<br />
Fisure 3.<br />
l.lGEk Ardel Loed<br />
Comprg8sion<br />
KN<br />
12<br />
10<br />
8-<br />
I<br />
4<br />
2<br />
Neck Ltrd I I<br />
-----___*jl<br />
0<br />
3600 3650 3700 3750 3800 3850 3900 3950 4oOO<br />
nme In Miiltsoconds<br />
FootCrush<br />
Foof Crurh<br />
Milllmeler8<br />
Figure 3. Estimated Relationship Between Pll7L4 Roof<br />
Crush and Head Strike Timing<br />
Onc clear conclusion from the GM lests is that a<br />
strongcr roof, which does not collapse, changcs the<br />
tlynamics of the rollover $o thilt far sidc roof rail conlact<br />
is lcss severe and thsrsfore less injurious. In both sets of<br />
production vehicle tests when the roof collapsed thc<br />
magnitude of tho far side neck comprcssion load was as<br />
high ns 13.200 ncwtons, uften excccded 7000 ncwtons,<br />
but in both scls o[ lollcaged tcsts, the neck compression<br />
never cxcceded 6600 ncwtons.
tion 3: Technlcel Sessions<br />
<strong>The</strong>re were more PIIs (and a few > 4k newtons) on the ' <strong>The</strong> erect dummy ncck is probably not rcpresentrtive<br />
near side of the rollcaged than production vehiclcs, the of a persons neck in rollover impacts, nor repre-<br />
magnitude of the hits arc mostly mitigatable.<br />
Countermeasares. CM published no commenl on how<br />
sentative of human reflcx actions:<br />
' <strong>The</strong> far side occupant is much better off with a non-<br />
mitigation measurcs would effcct the injury results of the collapsing and strengthencd roof (although a 160#<br />
3200 pound 1983 Chevrolet Malibu rollover tests. <strong>The</strong>y rollcage is not nece.ssary);<br />
were considered in this study on a group and individual . A stronger roof structure alone is not sufficient to<br />
basis and the applicability of alternate designs were eliminate the potential for critical injurics for all<br />
determined. An assessment of the ability to significantly<br />
mitigate each of the injury impacts was made using<br />
occupflnts;<br />
. Roof collapse increases the potcntial for critical<br />
Metric 3 as the evaluation criterion. Since most roof<br />
contact velocities in the GM tests were between .8 and<br />
injury by increasing the cffective hcad conritct<br />
velocity; antl,<br />
3.3 m/s, we concludcd that if the roof could be . While torso augmentation is a significant factor in<br />
$trengthenedjust enough to resist collapsc as occurred in<br />
the Number I unrestrained and the Number I belted convenlional<br />
roof tests, the padding would mitigatc the<br />
remaining interior neck compression forces.<br />
Of course, in addition to the larger gauge-and-section<br />
roof support strengtherring design and adcled metal<br />
padding, the countermeasure system should include<br />
some conlacts with an unpadded roof, thc contilcts<br />
frequently occur when fhe roof is not yct displaced,<br />
nor in contact with thc ground, making padrting<br />
countcrmeasures 0ffcctive.<br />
Head Strike, Padding and Computer<br />
Sitnulations Studies<br />
retained and improved side glazing to limit ejection.al<br />
<strong>The</strong>se results are shown in Table 7.<strong>The</strong> total production<br />
weight increase of this countermeasure system is estimated<br />
to be less than .50 pounds.<br />
Table 7. Results of GM Tests Gonsidered with<br />
Appropriate Countermeasures Showin g Expected Number<br />
of Potentially Critical InJuriee<br />
A numher of indcpendent real world injury accident<br />
studics were conducted or reviewed in conjunction with<br />
head and neck injuries in other accidcnt modes to<br />
validate Injury Measurc rcsults and confirrn the effects<br />
of padding. <strong>The</strong>se included:<br />
. three hclmeted football players receiving quadriplegic<br />
injuries through the inefficicnt l" of padding<br />
at the top of thc hclnret and strikc velocities in the<br />
Original<br />
potentlal<br />
Critical<br />
fnjury<br />
hpacts<br />
ExFected<br />
Nunber Of potentlsl<br />
critical Injury<br />
Inpacts with<br />
Counterneasures<br />
I to l2 ftlscc range. <strong>The</strong>se cascs had the advantage<br />
of filmed occurrcnce on a marked grid, physical<br />
dummy tssts and 2 and 3 D corrcsponding computer<br />
simulittions.<br />
EtandErd Far slde<br />
Roll cage Fsr elde<br />
B/E<br />
6/8<br />
O/B<br />
O/B<br />
. five side impact car citses involving hearJ studies on<br />
Standard Nearsids<br />
RoII cage Hearside<br />
3/E<br />
5/B<br />
E/B<br />
o,/e<br />
. inadequiltely paddcd roof rails and sail panels;<br />
r a plrametric computer study of a far side, side<br />
Rollover Tests Relative to Real Warld Accident<br />
Studies. This analysis of GM rollover tests has provided<br />
injury measure insights, one test relative to another, but<br />
a comparison to actual case work studics has ,shown f hat<br />
the test conditions used are not rcprcselltative of real<br />
world accidcnts since:<br />
. Many rollovers have a violent yaw maneuver prior<br />
to the initiation of roll causing the far side occuplnt<br />
impact occupflnt contacting lr conventional and/or a<br />
padded roof at vcrtical velocitics of 2 to 3.5 m/s,<br />
horizontal vclocities of 0, +7/-2, +/-4 meter/sec and<br />
0o, l0o and 20o hcad flexion3?;<br />
. onc case of'a fronlitl hcad strike on a passenger side<br />
GM<br />
to move forward and toward whnt will become the<br />
near-sidc occupanU<br />
. Thc dummy is launched wirh about a l0 ft/sec<br />
vertical velocity vector from the dolly which ciruses<br />
unrestrained dummies and several of the dummies in<br />
the restrained tcsts to move to the roof as the wheels<br />
touch down, and to incur signilicant injury mcasures<br />
suggesting risk of critical injury in the process;<br />
. <strong>The</strong> dummies cannot hold on and/or brace themselves<br />
as would be the reflex action of people in<br />
impacts;<br />
-'X" car instrurnent pilnel whose force/dcflcction<br />
properties yicldcd effectively 4" of srroke;<br />
. NHTSA study on head strikes and A pillar padrling<br />
effectivcncs$'<br />
l:-33' 4r<br />
. OM study on A pillar and roof rail padding;n<br />
. GM drop tests of restrained and unrestrrincd l{ybrid<br />
III dummics in convcntional and rrrll caged r
13h|fr lntemetlonel Technlcal Conference on Experlmentel Safety Vehicles<br />
measure approach is thc monocoque rounded roof structure<br />
of thc Minicars Rcsearch Safcty Vehicle which<br />
rollcd three times without excessive far side roof rail<br />
acceleration or deformation. It provitlcd 4 inches of roof<br />
dcformation without intruding on the occupant's survival<br />
spacs. <strong>The</strong> angled interior roof contirct surfacc was<br />
designed to flex the head and neck to preclude axial<br />
loading.<br />
Figure 4. Re$eerch Salety Vehicle<br />
A case example involves a heavy 220# man, unrestrained<br />
in a partial (20-30 dcgrec) roll as thc rcsult of<br />
a far side, side impact. <strong>The</strong> vehicle and ncar sidc occupant<br />
motion resulted in an effective vertical contact<br />
velocity of about 2.5 meters/second with the roof, producing<br />
C5-C6 quadriplegia.<br />
<strong>The</strong> first thing done37 was to conduct a paramctric<br />
analysis of the possibilities for dummy neck injury when<br />
striking a roof at various vertical and horizontal<br />
velocitics and with various head orientations. We also<br />
considcrcd thc very same circumstances but with a<br />
mathematically padded, non-pockcting roof. <strong>The</strong> results<br />
indicated that at 2 to 3 m/s contact velocities ncck<br />
compression injury measures could be limitcd to the<br />
2500 newton range.<br />
Next an exemplar car was located and thc static<br />
forcc/dcflection properties of the roof were measured<br />
with a hcad form. A 22 gauge plate with l" high tabs on<br />
6" celrters werc thcn inserted between the headform and<br />
the roof and the mcasurcmcnts repeated. <strong>The</strong> measurements<br />
are shown in Figure 5.<br />
This data shows that thc lincd roof limits the force to<br />
about 500 pounds (2200 newtons), over 800 inch-pounds<br />
of energy absorption, while the conventional roof<br />
exceeds 500 pounds at 400 inch-pounds. Translated to<br />
case related neck compression injury meflsurcs, as shown<br />
in Figure 6, it means that a paddcd roof can limit neck<br />
forces trr below 2500 newtons at up to l40To of the conventional<br />
roof's acceptable (? to 3 m/s) contrrct velocity<br />
or, when at the samc speed, the conventional roof produces<br />
15,000 newtons, the paddcd roof will limit to less<br />
than 2500 n.<br />
7ffi<br />
Force<br />
(N)<br />
6000<br />
4000<br />
2000<br />
{F,bJHE[lEiflHF<br />
0<br />
Displacement (in)<br />
Figure 5. Force/Deflection Properties ol a Typical<br />
Passenger Vehicle Roof and With 1'lnch Tabs on six-lnch<br />
Genters on a 22 Gauge Metal Inner Rool Liner<br />
3-D Test Nunber 105 106 102<br />
Roof characteristlc BaBellne Basetlne Padded<br />
vlctln Roof contact vetodlty z fr/s 2,5 ilr/s 2,5 m/a<br />
Inltlal<br />
fix" velosLty 2,o e'0 2,0<br />
Inltlal'ry" veloclty 4-o 4.O 4-o<br />
Initial Hcad Angls 90 90 90<br />
Inltial Neck Angle 90 9o 90<br />
Head to Roof (Lbs) 485 5000 406<br />
Neck ConFteEsioh (IbE) 37O 4L4? 303<br />
Force<br />
(lbs)<br />
Figure 6. <strong>The</strong> Comparatlve Characteristics and Dummy<br />
Injury Measures for this ca$s, Derived in 3'D from<br />
Figure 5 Mea$urement$<br />
Summary<br />
A loss of directional control resulting from the vehicle<br />
response to a cotnbination of cmcrgency steering and<br />
braking inputs initiates lateral skidding and rollover<br />
accidents.<br />
Data analysis shows significantly grcatcr risk of<br />
critical injury when an occupant is in thc proximity of<br />
roof crush with deformfltion extent index grcatcr than 3.<br />
Case study analyscs show that occupilnts under a<br />
crushed roof scction suffer more severe injurics than<br />
those not under a significantly crushcd rottf section.<br />
GM test data shows a significantly greater chance of<br />
critical injury whcn an occupanl is under a crushed roof.<br />
Previous puhlishcd inlormation obscured facts by using<br />
a low threshold of --potential injury" rathcr than a<br />
mcasure consistent with criticfll injury.<br />
<strong>The</strong> risk of hcad/ncck injury from roof contact in<br />
rollovers is related to the rclfltive contilct velocities of<br />
the head/neck, and the orientation of thc hcad, neck and<br />
tOrso upon contact with thc roof.<br />
Risk of critical head/ncck injury is dependent on:<br />
. roof intcrior hcad/neck clearance<br />
. roof shapc<br />
I extent >3 of roof dcformation<br />
. intcrior forcc/dcflcction characteristics<br />
. reslraint system performance<br />
. glazing performancc
<strong>The</strong> results suggest that such alternative rollover<br />
safety design improvcmcnts. adding approximately -50<br />
pounds to the vehicle weight and $2-50 in cost. could<br />
save as many as 5000 lives pcr ycar and 5000 critical<br />
neck injuries in all accidcnt modes.<br />
BENEFIT6<br />
cosTS<br />
FATAIJITIES EI'IMINATED<br />
CRITICAL TNJURTES REDUCED<br />
SEVERE INJURIEB REDUCED<br />
HETGM<br />
cosr<br />
5000<br />
2 500<br />
2500<br />
50 lbr<br />
s250<br />
Figure 7. Eetlmated Head/Nsck Inlury Countermeesure<br />
and Benefit/Cost in AllAccident Modes<br />
Further and more detailed observations, comments and<br />
conclusions are in APPENDIX C.<br />
Recommendations<br />
<strong>The</strong> roof support structure should be strengthened to<br />
avoid buckling collapse.<br />
<strong>The</strong> interior of all roof and roof support surlaces<br />
should bc paddcd with force Iimiting mrterirrl to allow<br />
two inches of deformation at 2500 to 3500 ncwtons without<br />
pocketing.<br />
Rcstraint systems should be equipped with emergency<br />
tensionin g rctractors.<br />
Side window glazing should be laminated and retained<br />
to reduce roof deformation, shattering and linrit cjection.<br />
Anti-lock Braking Systems should bc insttlled to<br />
improvc cmcrgency dircctional conlrol thercby reducing<br />
the frequency of rollover accidents.<br />
References<br />
1. Fatal Accident Reporting System (FARS), NHTSA.<br />
2. National Crash Severity System (NCSS), NHTSA.<br />
3. National Accident Sampling System, (NASS),<br />
NHTSA.<br />
4. <strong>The</strong> Severity of Rollover Crashes in the National<br />
Crash Severity Study; Robert McGuigan, December<br />
1980.<br />
5. Light Truck and Passcnger Car Rollovcr and Ejection<br />
in Single-Vehicle Crashes, Kenncth W. Tcrhune,<br />
PH.D. Arvin/Calspan.<br />
6. Statistical Estimation of Rollovcr Risk; Pcter<br />
Mengert, Santo Salvatore, Robert DiSario, Robert<br />
Waltcr, August 1989.<br />
7, A Scarch for Priorities in Crash Protection: SAE<br />
820?.42, Malliaris et al, page 6 &,7.<br />
8. Crash Injury Impairment and Disability: Long Term<br />
Effects, SAE SP-661 860505 S. Luchtcr, pagc 94 &<br />
96.<br />
9. Cervical Injurics Sutfcrcd in Automobile Crashcs, J.<br />
Neurosurg. March 81, Mendelsohn et al p. 316.<br />
10. Head Injuries in Highway Accidents-Cuncnt<br />
Incidence and Potential Abatcmcnu Malliaris and<br />
Digges, Univ. of Virginia, 1991.<br />
Sectlon 3: Technical Sessions<br />
I l. Advanced Norice of Proposed Rutemaking for<br />
FMVSS 214 February 199I and Arrrendrnent to<br />
FMVSS 216 Docket No. 89-22, April 1991.<br />
12. <strong>The</strong> Crash Avoidance Rollover Study: A Database<br />
for the Investigation of Single Vehicle Rollover<br />
Crashes; E. A. Harwin, Lloyd Ernery, May 1989.<br />
13. Comparative Evaluation of [tollover Rates, Prepared<br />
by Data Link, Inc. CONFIDENTIAL, not publicly<br />
available.<br />
14. Rollovcr Potential of Vehiclcs on Embankments-<br />
Sideslopcs, and Other Roadsidc Fcirlurcs August<br />
1986 Final Rcports; Federal Highway Administrution-Office<br />
of Research and Development, Note:<br />
Vol. I and II. File dated Novemher 1986. Also SAE<br />
870234.<br />
15. Injury Assessment Values used to Evaluate Hybrid<br />
III Rcsponsc Mcasurcrncnts; Harold J. Mcrlz, Stfcty<br />
and Crashworlhincss Systcms. Currcnt Product Enginccring,<br />
Gcncrtl Motors Corporation, Feb. 1984.<br />
16. Injury Critcria tnd Mathcmtticirl Anirlogs for Selectcd<br />
Body Arcas; Roll H. EpJringcr, NHTSA, July 6,<br />
l9tt2.<br />
17. <strong>The</strong> Bionrechrnics of Ncck Injury from Direct<br />
Impact to the Hcad; V. R. Hodgson, L. M. Thomas,<br />
Hcad and Ncck Injury Critcria-Consensus Wolkshop.<br />
18. Kinematic and Anatomical Analysis of the Human<br />
Cervical Spinal Column Undcr Axial Loading:<br />
Pintar, Yoganandln, Sances, Reinrrtz, Harris and<br />
Larson SAE 892436.<br />
19. Epidemiology and Injury Bionrechanics of Motor<br />
Vchiclc Relatcd Trauma to the Human Spine;<br />
Haffner, Mairnan, Pintar, Yoganandan, Sances,<br />
Nichols. Jentzen. Weinshel and Larson SAE 892438.<br />
20. NHTSA Rollovcr Tests: Vchicle lnd Dummy Kinentatics<br />
in a Controllcd Rollovcr Crash-l) 1988<br />
Chcvrolct Standard Rcguhr Bed Pickup, 2) 1989<br />
Nissrn Standard Regullr Bed Pickup, 3) 1988 Nissan<br />
Standard Regular Bed Pickup,4) 1989 Nissan<br />
Pickup Truck. -5) 1989 Nisstn Pickup Truck; Trtnsportation<br />
Research Ccntcr of Ohio.<br />
21. Vchicle lnertial Pararnelers-Measured Values and<br />
Approximations-SAE Tcchnical Paper Selics, W.<br />
Rilcy Garrott, Mickacl W. Monk, Jeffrey Chrstos<br />
Date. October 3l-Novcnrber 3. 1988 SAE #: 881767.<br />
22. Slatus Rcport on NHTSA Sponsored Research on<br />
Computer Modeling of Rollovcr Vchiclc Dynarnics,<br />
Presentation to Rollover Subconrnriilee. Motor<br />
Vehicle Safety Research Advisory Committ0c,<br />
NHTSA, March 16, l9lt9; Andrzcj G. Nalecz..<br />
23. NHTSA Reserrch Safety Vehicle (RSV), Phase I,<br />
t974. DOT-HS4-00844. Phase II. 1975. DOT-IIS-5-<br />
01215, Phrtsc lll, 1977, DOT-HS-7-01552, Phase IV.<br />
1978, DOT-HS-8-02096, Minicius, Inc.<br />
24. Occuprnt Motion During a Rollover Crash; Arnold<br />
K. Johnson, David A. Knapton NHTSA, Novembcr<br />
1984.<br />
761<br />
I<br />
-f,<br />
;
lSth lnternatlonal Technlcal Conference on Experlmental Satety Vehlcles<br />
25. Roltover Crash Tests-<strong>The</strong> Influence of Roof Strength<br />
on Injury Mechanics; Kenneth F. Orlowski, R.<br />
Thomas Bundorf, Gcncral Motors Corporation;<br />
Edward A. Moffat, Biomech, Inc. SAE 851734.<br />
26. Rollover and Drop Tests-<strong>The</strong> Influence of Roof<br />
Strength on Injury Mechanics using Bcltcd<br />
Dummies; G. S. Bahling, GIvVCPE, R. T. Bundorf,<br />
GIvVCPE, G. S. Kaspzyk, GIWCPE, E. A. Moffatt,<br />
Consultant, K. F. Orlowski, Consultant, J. E. Stockc,<br />
CM/CPE; SAE 902314.<br />
27. Real World Rollovers-A Crash Test hocedure and<br />
Vchiclc Kinematics Evaluation; T.M. Thomas, N.K.<br />
Coopcrridcr, S.A. Hammoud, P.F. Woley, Failure<br />
Analysis Associates, Inc., March 10, 1989.<br />
28. Rcconstruction of Rollover Collisions, K.R.<br />
Orlowski, E.A. Moffatt, R.T. Bundorf and M.P.<br />
Holcomb SAE #: 890857.<br />
29. Rollover and Interior Kincmatics Test Procedures<br />
Revisited; John L. Habberstad, Roger C. Wagncr,<br />
Terry Thomas SAE #: 861857.<br />
30. Testing and Analysis of Vehicle Rollover Bchavior;<br />
Neil K. Cooperrider, Terry Thomas, Sclim A.<br />
Hammoud, Test and Engineering Center SAE #:<br />
900366.<br />
31. Development of a Tumble Number for Use in<br />
Accident Reconstruction: Thomas A. Bratton SAE #:<br />
890859.<br />
32. Side Interior Stiffness Measurements; Donald T.<br />
Willke and Michael W. Monk, NHTSA SAE 861880.<br />
33. Injury and Intrusion in Side Impacts and Rollovcrs;<br />
Charles E. Strothcr, Greg C. Smith, Michael James,<br />
Charles Y. Wiuner Collision Safety Engineering,<br />
SAE #: 840403.<br />
34. Prediction of an Occupant's Motion During Rollover<br />
Crashes; Louise A. Obergefell, Ints Kaleps, Arnold<br />
Johnson, NHTSA SAE #: 861876.<br />
35. MVMA 2-D Modeling of Occupant Kinematics in<br />
Rollovers; D. Hurley Robbins, David C. Viano SAE<br />
#: 840tt60.<br />
36. Live Subject Safety Research-Side Impact; Donald<br />
Friedman, S. Forrest, F. Gott, and G.D. Dyne-Liability<br />
Research, Inc. SAE #: 890382.<br />
37. Improved Product Dcsign by Impact Testing of<br />
Human Subjects, D. Fricdman, lttth Intcrnational<br />
Workshop on Human Subjects Biomechanical<br />
Research, November 1990.<br />
38. <strong>The</strong> Safe Road to Fuel Economy; D. Friedman, K.D.<br />
Fricdman, Clarcncc Ditlow and D. Nelson, April<br />
199 l.<br />
39. Large Car-Small Car Offset Crash Test at 70 mph<br />
Closing Speed with Air Bags; Insurance Institute for<br />
Highway Safcty, Brian O'Ncill, Fcbruary 1991.<br />
40. Statistical Analysis of Injured Occupants by Seating<br />
Position & Location of Roof Deformation; Keith<br />
Fricdman, Donald Fricdman, unpublished.<br />
762<br />
41. Sub-System and Full System Tcsting to Assess Side<br />
Impact Safcty; D. Willkc, D. Cuenther, M. Monk,<br />
18983. SAE #830465.<br />
42. Comparison o[ New Car Assessment Program Crash<br />
Test Results with Real World Crash Test Data;<br />
NHTSA Rulcmaking Office of Market Incentives,<br />
March 1988.<br />
43. Car Crash Tests of Glass-Plastic Side Glazing, Carl<br />
Clark. Pcter Sursi. 1984.<br />
44. General Motors Vchicle Safety Improvement Program<br />
(VSIP) Confidential, Unpublished.<br />
45. U.S. Patent Numbcrs 4285479, 4023746,4684077.<br />
4540t37.<br />
46. Biomechanical Evaluation of thc Axial Comprcssive<br />
Responses of the Human Cadavcric and Manikin<br />
Necks; N. Yoganandan, A. Sitnccs, F. Pintar, August<br />
1989.<br />
Appendix A. Statistical Methodology<br />
<strong>The</strong> availability of the Nationul Accident Sampling<br />
System" represents a substantial r-csourco for tho culculation<br />
of nationally representative drta associalcd with<br />
crash conditions and consequences. While the data is<br />
available lrom 1979 through the prosent, two years of thc<br />
data (frorn l9lt2 and 198-l) were selected for use in this<br />
study due to their similirrity of filc formats which<br />
simplified the formulation of working data sets. Thc<br />
effort required to process the additional ycars availablc<br />
has been left for further study.<br />
In order to put the data into a fonn consistent with the<br />
analysis requirements the files were:<br />
l. Convcrted to an occupant level file<br />
2. Filtcrcd for occupant vehicle rollover involvement<br />
Variable I 12 in 1983 Vehicle Record Format<br />
3. Filtered for Unknown Data<br />
a) Known Maximum Injury Level Variable 98 in<br />
1983 Occupnnt Rccord Format<br />
b) Known Rollovcr Dctails (Exclude 3 on Variable<br />
I l2 on l9lJ3 Vehicle Record Format)<br />
c) Passcngcr Compartrnent Integrity not equal 0 (O<br />
= no passcnger cotnpartment) (Exclude 0 on<br />
Variable 106 of 1983 Vehicle Record Format)<br />
d) Exclude non-passenger c[lrs and convertiblcs<br />
(Exclude all but 2-9 Vehiclc Body Type on<br />
Variable 23-24 in 1983 Vchiclc Rccord Format)<br />
e) Known Mtgniludc of Intrusion Variable l0ll in<br />
l9ll3 Vchiclc Rccord Format<br />
f) Known Firs,t Collision Delbrmittion Clrrssification<br />
for General deformation location (see Figure<br />
bclow)<br />
Longitudinal/lateral Iocation<br />
Vertical/lateral location<br />
Type of damage Distribution<br />
Deformation Extent
g) Occupant seflt positions 1,3,4,6,7,9 (no<br />
occupants in mid seat locations and no unknown<br />
scat positions)<br />
Cases with non-top damage greatcr than 4 were not<br />
considered. Occupants who were totally ejectcd through<br />
the door were not considered.<br />
canatal Sprolllc ToP Ep.elflc ToE<br />
OccuFant DaDtrg€ ldngltudlnal Dabage Iateral Danage<br />
Lft 61d16 Eop centor Dlatrlbutad<br />
cent€r & Pront Iaft<br />
C€ntar * Roar Isft E centar<br />
Dlstrlbut6d<br />
Rtgtrt Sld6 Sop Ccnt.r Dl8tributod<br />
cEnter & Front Rtght<br />
C€nt€r & R€er Elght & CenteE<br />
Dletrlbuted<br />
Variables of interest in the files were recoded where<br />
necessary to provide for consistency betwccn ycars; aftcr<br />
this was done, the files were merged into onc filc.<br />
Following the creation of the analysis data file<br />
exploratory analysis of the data was conductcd. Various<br />
factors were examined to assess the significance of thc<br />
factors on injury consequences. <strong>The</strong> Statistical Analysis<br />
System package was used for all analysis work. Brsed on<br />
initial work new variables were creatcd combining various<br />
variables into physically sensiblc combinations<br />
rcflecting the considerrtions inherent in the hypothesis<br />
undcr investigation.<br />
Aftcr initial rcviews of the data. cases were selected<br />
for revicw of thc underlying hardcopy records to gain<br />
additional insight into the implications of the coding<br />
procedurcs in use.<br />
Thc hardcopy review aided in identifying rollover<br />
types and the nature of damage associated with thc<br />
occurrence of injury. <strong>The</strong> rcsults suggcst that roof<br />
damage descriptions relative to occupant locations would<br />
correlate with severe injury occurrence. It was also noted<br />
that cjection and ejection paths may also be related to<br />
roof crush and distortion or may be a secondary effect<br />
relative to the rooI crush. <strong>The</strong> study suggested among<br />
other things that:<br />
. Cases with significant roof crush at the occupant<br />
location or expected contact area appear to generally<br />
result in substantial injury.<br />
. Cases with substantial other damage may distort data<br />
analysis results (e.g. frontal or side imprcts in which<br />
there was also a rollover).<br />
<strong>The</strong> final analyses took into account the abovc considerations.<br />
It was also recognized that detail at thc lcvcl<br />
of thc hardcopy cases for the classification of roof crush<br />
would yield substantially better precision witlr rcgrrd to<br />
thc location and amount of the roof crush relative to the<br />
occupant.<br />
While confidence intervals can be calculated for the<br />
data, substantial effort is rcquired. As a result, it was<br />
decided for this analysis to observe the consistcncy of<br />
Section 3: Technical Sessions<br />
the results across analyses and across altcrnative injury<br />
level thresholds. Depending on thc rcsults of the analyses<br />
further work on fornral conl'iclence intcrval cstination<br />
may be desirable to establish statistical signil'icance.<br />
Howcver, in the event of large difterences in probahility<br />
or in the case whcrc the rclations arc consistently upheld<br />
the likelihood is that the liuge effort requircd to compute<br />
the confidence intcrvals would not be justified particularly<br />
when more data can bc added to simply enlarge<br />
sample sizes.<br />
Based on the exploratory and hardcopy analysis results<br />
a variablc was crcatcd to rcflcct lhe general proximity of<br />
damage to the occupant location. <strong>The</strong> general form ol'the<br />
variable was dependent on the occupant location as<br />
illustrated below.<br />
<strong>The</strong> proxirnity coding was assumed as shown bclow<br />
such that cascs mecting these requirements were considercd<br />
to bc in thc proxinrity of roof damage (and<br />
otherwise thcy wcrc not).<br />
It is clear that thi$ coding scheme can, of course, be<br />
refincd. Further, the uddition ol' lretter precision in the<br />
data througlr lhc usc of the hrrdcopy results to inrplement<br />
a nrorc dctailcd coding scheme may prtlvide for<br />
bcttcr rcsolution in the anrrlysis of the data. Presurnahly,<br />
the additionitl prccision would make the difference in the<br />
rcsults discusscd in the paper even more pronounced.<br />
Appendix B. Detailed Driver and Passenger<br />
Head/Neck Contact Loads in GM Rollover<br />
Tests<br />
TPPENDIX B - Unejoctad, DRIVER h€ad/n6ck contBct lordB fro! 16<br />
6l.l Rlght RoIIovGr t68te (8 Rsstralned and I Unrastralned)<br />
TEST COTIDITIOil AXTAT NECK IdADA NECX I,TOI.IENES HIC<br />
PII Atd Hax >skn+lkn flex>t90m<br />
I Standard Roof >zkn >4kn kn Bhear lat,sxt>5?il<br />
4<br />
7<br />
I<br />
taBt/dr 5 3 r?, I 3lat 90<br />
rGEt/dr /t { 7.s I I flsx 3 tat 200<br />
rest/dr 1 Z 13.? ? Z1at 740<br />
rdst/dr 2 2 5.3 1 zlat 6{0<br />
Subtotal<br />
l a u n r E / d r 3 1 5 . t I 3 a B Z O<br />
4a unri/dr 4 3 7,A 1 I nlil<br />
5r unrE/dr t 1 {.5o o o n/e<br />
8n unrF/dr 4 3 s.to O o fSO<br />
Subtotal<br />
Iotal fiulbar ><br />
rf,<br />
TEST CONDITION AXIAIJ NECK rcADS NECK MOffEHTA HIC<br />
PII std tax >skn+lkl flex>l9Onn<br />
I Rollcage Roof >2kr >4kn kn ahear latfext>s7nb<br />
I<br />
5<br />
6<br />
r e s t / d E 0 0 0 O b 3 O<br />
r e E t / d r 1 1 5 . 6 0 0 , t 2 0<br />
r e s t / d r 0 0 0 O B o<br />
rert/dr 3 1 ,t.l O I lat 130<br />
Subtatal<br />
2e unre/dr<br />
3a unrB/dr<br />
6a unrs/dr<br />
7a unr6/dr<br />
Subtotal<br />
TOTAL NI'Ii'BER ><br />
6 2 4 , 9 0 0 3 3 0<br />
l l 5 . o 1 ? o k<br />
? 1 4.8 O 0 ^/d<br />
t I 5.7 0 I 100<br />
l4
13th lnternetlonal Technlcal Conferenee on Experlmentel Sefety Vehlcles<br />
APPENDIX B - PASSENGER head/neck contact loads frofi 16 CM Rlght<br />
Rollovsr t6sts (A Rratralned And I Unr€atral-n6d)<br />
TE6I CONDITION HTAIJ NECK MADS NECK UOMENTS HIC<br />
PII Std I'lax >Ekn+1kn flax>lgonn<br />
* standard Roof >zkh >4lrn kn Bhear lat,ext>s7nm<br />
3 reBt/rfp<br />
4 rBst/tfp<br />
7 ref,E/rfFl<br />
I rest/rfp<br />
Subtotal<br />
lE unrs/rfp 5 t 4.6 0 0 (3 ground) 640<br />
4a unrs/rfp 3 2 7.8 I 0 (2 ground) n/a<br />
5a unre/rfF 3 o 3.8 o 0 (z,tqrd/e)\n/a<br />
8a unrs/rfp e O Z,Z O 0 140<br />
Su.btotal<br />
Total Nuhb6r ><br />
0 0 0 0<br />
I 2 4.a 0 0<br />
3 1 4-75 0 0<br />
0 0 0 0<br />
TEST CONDITION AXIAI. NECK INADS NECR HOMENTS HIC<br />
PII Std l{ax >skn+lkn fl.x>tgonn<br />
# Rollcage Roof, >2kn >4kn kn Eh6ar lat,ext>sznm<br />
1 rest/rfp<br />
2 telt/rfF}<br />
5 rest/rfp<br />
6 rast/rfp<br />
4 1<br />
3 r<br />
6 2<br />
t 0<br />
6<br />
4.5<br />
2.3<br />
0 0<br />
o 0<br />
1 ?<br />
o 0<br />
90<br />
IOO<br />
70<br />
160<br />
200<br />
180<br />
r30<br />
190<br />
?a unrs/rfp 2 0 0 o (lground) z8o<br />
3a unr6/rfp 4 0 O O (3ground) 24o<br />
6e qnre/rfp 3 I 4,5 O I (1 ground) n/a<br />
7a unrs/rfp 5 1 4.8 0 0 (t ground) 1Io<br />
Tota1 Nuh.ber ><br />
Appendix C. Other Observations, Comments<br />
and Conclusions<br />
More effort should be made to utilize the real world<br />
data available, to identify safety problcms and to<br />
improve vehicle product safcty dcsign.<br />
Crash pulses with longcr rolls and lower angular<br />
accelerations appear to result in reduccd risk of occupant<br />
injury. Such pulses are charactcristic of roofs shaped like<br />
the Minicars RSV, cius of the 1950's and some current<br />
sporty cars.<br />
In rollover impacts, the roof edge (corner) frequcntly<br />
experiences rolling contact with the ground, whcn thc<br />
translational velocity at touchtlown is 5 or morc mph<br />
higher than the roll rate timcs thc roll radius, resulting in<br />
a low (3 to 4g) long duration, or a high (10 to 20g) short<br />
duration shearing force at the roof rail. <strong>The</strong> conscqucncc<br />
is to plow a I to 2 foot ground patch, collapsing the<br />
leading side "A and B" pillars towards the center ol the<br />
vehicle, shifting the roof and destroying thc intcgrity of<br />
the trailing pillars leading to their comprcssion buckling.<br />
<strong>The</strong> shape of the roof of current cars is thought to bc<br />
inviolatc, but they could easily have more rounded roof<br />
rails and grcater tumblchome, allowing the cars to roll<br />
more easily with less peaked latcral dccclcrlrtion. A<br />
monocoque roof design should improve rollover crashworthincss<br />
at lower cost and weight than present designs.<br />
A squared, rollcaged roof edge radically altcrs thc<br />
dynamic roll rate, vertical and lateral vclocity and<br />
occupant conlact vclocity.<br />
In rollover impacts, occupants seated under a portion<br />
of thc roof which crushcs arc at significantly grcatcr risk<br />
of critical injury than those seated under a roof without<br />
significant roof crush.<br />
7ffi<br />
In rollovcr impacts Iimiting roof crush to l few inches<br />
(detormation index of 3 or less), signiticrnlly rcduccs<br />
thc risk of critical injury.<br />
S trongcr rooI sl.ructures:<br />
. change the kinomiltics and dynamics of rollovers<br />
. allow morc vchicle energy to be absorbed in translation<br />
rather than in the crushing of thc roof and hcnce<br />
not adding to the occupant's hcrd and ncck vcrtical<br />
contact vclocity<br />
. reduce the occurrence of in.lury lneasures associated<br />
with critical injury for far sidc occupants<br />
Roof crush is rcsisted not only by the structure but by<br />
the strcngth o[ thc windshicld and closed side windows.<br />
Any structural roof crush in the area of conventional<br />
side glazing produces brcakage allowing lhc potcntial for<br />
subsequent head ejection and contact with thc ground.<br />
Stronger roof structures provide for thc irbility to<br />
retain windshield and irlprovcd sidc gltzing, and thcy in<br />
turn increase roof strength.<br />
A rounded, mildly dcfolrning roo[, rolls ntorc snroolhly,<br />
resulting in lowcr instantlncous decclcrations, lower<br />
occupant contact velocitics and potcnlially lcs,s injurious<br />
impacts with the intcrior.<br />
Most current roofs only need nlinor struclural chtngc<br />
to limit deformation extent and itvoitl collapsc and<br />
injury.<br />
Gencral Motors utilized a low injury meir$ure threshhold<br />
to conclude that there is no diftcrcncc in occupanl<br />
injury whether the roof crushcs or not. Thcir usc of a<br />
"potentially<br />
injurious" critcrion rather lhan thc potcntial<br />
for critical injury, would appcflr to rttislcad rcgrrlllors<br />
into believing thilt il strongcr rool' with I'orce lirniting<br />
interior is unnecessary.<br />
A "potentially injurious" critcrion may bc consislcnt<br />
with corporate objectives for minirnizing costs but highlights<br />
the differences between nurnulaclurcr corporate<br />
objectives, insurancc cornpilny objoct ivcs of nr inirrr izing<br />
injury costs, and govcrnmcnt objcctives for naxinrizing<br />
overall socictal trcnclit.<br />
<strong>The</strong> scatcd, track inclined, hody position sigrrificantly<br />
reduces potentiill neck loading lrorn thc turso.<br />
<strong>The</strong> contact vclocity and cncrgy of thc torso in rollover<br />
collisions is low relative lo the interiur, and hetd<br />
and neck orientation is usually not aligned, so "torso<br />
augmcntfllion" ol' axial compressiolr injuries iue improbable.<br />
Increased usrge of scal bclt shouldcr hrrncsscs rnay<br />
substantially increase the risk of axial conrpression neck<br />
in_juries in current collapsible roof vehiclcs, by guir.ling<br />
the alignment of the head/neck with thc intruding rcrof<br />
surfacc.<br />
Uppcr vchiclc intcrior contact surfaces with 2" of<br />
force limiting "padding" would significantly reduce the<br />
potential for critical head/neck injuries.<br />
Strcnglhcning the roof slruclurc in all cars so thflt they<br />
won't buckle or collapse tfter bending and absurbing<br />
energy for a few inches will elirninate lnore than -50% of
the paraplegic/quadriplegic level injuries in thc rollover<br />
accidcnt population.<br />
History has shown that a regulating authority or the<br />
consumer has to rcquire improvcil safcty. NHTSA and<br />
GM cxpresscd cnthusiasm for the Airbag in 1970. Whcn<br />
rcgulatory implcmcntation was dclaycd, it took until<br />
1984 to requirc by l9tt7, thc 1974 GM ACRS driver<br />
s6.w.t2<br />
Effect of Car Size on the Frequency and<br />
Charles<br />
J. Kahane<br />
National Highway Traffic Safety<br />
Administration<br />
Abstract<br />
Narrower, lighter, shorter cars have higher rollover<br />
rates than wide, heavy, long ones under the same crash<br />
conditions. During model years 1970-82, as ths milrket<br />
shifted from large domestic crrs lo downsized, subcompact<br />
or imported cilrs, thc flcct bccame morc rollovcr<br />
prone. Thc net effect of all car size changes since 1970<br />
is an increase of approximately 1340 rollover fatalities<br />
per year in the Unitcd Stiltcs. <strong>The</strong> mcthods of this report<br />
do not identify which individual vehicle size parameter<br />
(track width, curb wcight, wheclblsc, ctc.) is thc<br />
principal<br />
"cause" of rollovcr pronencss.<br />
Introduction<br />
Rollover crashes are a major safety problcm, resulting<br />
in about 4,500 fatalities a year to occupants of passengcr<br />
cars. This report analyzes the influence of car size on<br />
rollovcr propcnsity, crashworthincss and fatality risk.<br />
Thc issucs arc studicd in the context of the overall trcnd<br />
in fatality risk of unrestrained occupants of passenger<br />
cars of model years 1970-82 in rollover crashes, for<br />
those are the years in which pilssenger cars became substantially<br />
smaller in the United States.<br />
In 1989, the National Highway Trlffic Safcty Administration<br />
(NHTSA) published An Evaluation of Door<br />
Locks und Roof Crush Resistanre of Passrngrr Cars [5],<br />
which includcs a dctailed litcrature review and analyses<br />
of the effect o[ car size on rollovcr crash involvcnlcnts.<br />
<strong>The</strong> material in this report is cxccrptcd from lhc cvaluation.<br />
What Happened to Cars in 1970-82?<br />
It is ohvious that cars bccame<br />
"snraller"<br />
during 1970-<br />
82, but there are several ways to measure car "sizc."<br />
Thrcc mcasures of size that are often used in analyses<br />
arc curb wcight, wheelbase and track width. <strong>The</strong> paramcters<br />
arc highly intercorrelated, in that "large" cars<br />
tcnd to bc hcavy, long and widc whilc'-small" cars, wilh<br />
few exceptions, are light, short and nilrrow. For 1970-82<br />
Sectlon 3: Technical Sessions<br />
systcm pcrforrnancc in all csrs by I994. And during lhat<br />
interval. there wus much discussirln bctwccn NHTSA,<br />
industry spokesmen and the press about the practictlily,<br />
cffeclivencss and cosl ol' Airbags. Sincc aboul 1975 wc<br />
havc bccn tollowing thc sirnrc coursc to improvc sidc<br />
impact and rollover protcction for the head and neck. ls<br />
this necessary or approprintc to rneet satety objectives?<br />
Severity of Rollover Crashes<br />
cars, the correlation coefficicnts of curb wcight with<br />
whcclbase, curb wciglrt with track width and wheelbase<br />
with track width are .93, .92. tnd .91, rcspcctivcly.<br />
Bctwccn modcl ycars 1970 and l9tt2, thc nredian curb<br />
weight of cars in fatal crashes clccreased try about 1000<br />
pounds (fronr 1700 to 2700): thc rncdiirn wheclbitsc<br />
dccrcascd lly l() inchcs (fronr about ll5 to 105); and thc<br />
median trlck width, lly 2 or J inchcs (from 60 lo ilbout<br />
57). Since rnudcl year 1982, the pilrilmclcrs havc<br />
remained rather stable. At this tirnc (1990). thc sizc and<br />
weight ol thc avcrage car on thc road in the United<br />
States is close to the averlge rnodcl year 1982 car. as<br />
more and rnore pre-downsized cilrs ilre retired.<br />
<strong>The</strong> sizc rcduclions of lhs 1970-82 pcriod were<br />
achieved by two ntcchanisnrs. <strong>The</strong> rnorc inrporlant is a<br />
market shifl fronr l'ull-sizcd cars to subcompact and<br />
imported cars. Tho shift was alrcady undcrway in 1970<br />
and gained strcngth throughout thc pcriod. Secondarily,<br />
there was downsizing within many domcstic crr lincs,<br />
prirrrarily after 1975 (until l9'14, thcy wcrc slill<br />
growing). Irnports grew during the late 1970's and carly<br />
1980's.<br />
Factors Affecting Rotlover Proneness<br />
Thc l'ollowirrg cxanrplc ol'a sequence of events leading<br />
up to a rollover crash illusllutcs a variely of filclors<br />
affecting rollover. <strong>The</strong> first event is that thc drivcr,<br />
through inrllcntion or spccds in cxccss ol'clriving lbilitics.<br />
fails lo kccp llrc cur uirncd in lhc dirccliort o[ thc<br />
rorrdway. Upon ntlticittg thlt thc cur is atroul lo run off<br />
the road.lhc drivcr rnay lry drastic corrcclivc milncuvcr$,<br />
such as slamnring on lhc brakes or swerving. <strong>The</strong> attcrnpt<br />
is unsuccessful rnd puts thc car into a skirJ. Now it is<br />
hcading oft thc roldway with a partly sideways oricnliltion.<br />
After the car lclves thc rr.radway it cnc()untcrs<br />
tripping mechanisrns such as loose soil or a dilch,<br />
resulting in a rollovcr.<br />
'l'he<br />
preceding cxitmplc suggcsts that rollover propensity<br />
hils two componcnls, s0 t0 spcitk; ilirrrtittrtul<br />
stahility r.nd rollovu-slilbilily. A car is dir-cctionally<br />
unstablc il- it tends to skid or spin out of control or is<br />
hard lo slccr on coun;c. A dircctionally unstable car will<br />
havc mlny off-rord cxcursions into lcrrain whcre rollovcr<br />
is likely to occur. "Rollovcr stilbilily" is thc
13th lnternatlonal Technlcal Conference on Experlmental Sefety Vehlctes<br />
tendency of a car to remain upright giuen that it has<br />
comc in contact with a typical off-road tripping<br />
mechanism. Short light cars usually havc lcss dircctional<br />
stability than long, heavy oncs. Narrow cars havc less<br />
rollover stability than wide cars. Since "small" cars ilre<br />
shorter, lighter and narrowcr lhan full-sized cars, they<br />
tend to havc lowcr directional and rollover stirbilitv.<br />
Literature Review<br />
In 1968, Garrett studied the relationship of car sizc to<br />
rollover propensity [ 1 L defining the rollover rate of a car<br />
to be the ratio of principal rollovcrs to othcr singlc<br />
vehiclc crashcs. His idea is that rollovers and other<br />
single vehicle crashes typically involve aboul the same<br />
type of driver behavior-i.e., losing control of thc car<br />
and running off the road. <strong>The</strong> other singlc vchicle<br />
crashes act as a sort of control group and canccl out<br />
biases due to differenccs in driving cxposurc or<br />
aggressiveness. He pcrformed a rcgrcssion of the<br />
rollover rates of l9-50-67 ctrs by lrtck width. curb<br />
weight and height.<br />
--Thc data indicatc that thcrc is r<br />
strong correlation hetween rollovcr frcqucncy and<br />
vehicle dimensions: rollover incrcascs as car sizc shifts<br />
from heavy, wide track, low vehiclcs to light, narrow<br />
track, high cars. Car wcight and track width appear to<br />
havc thc grciltest influence on vehicle overturn."<br />
Jones [4], Griffin [2] and Harwin and tsrcwcr [3]<br />
performed similar regressions and obtained exccllent<br />
correlations of the rollovcr ralc with lhc'-stilbility factor"<br />
(half lhc track widlh divided by the height of the center<br />
of gravity) and wheelbase.<br />
Malliaris et al [6] emphasized the roles of directional<br />
stability and rollover stability as components of rollovcr<br />
risk. <strong>The</strong>y found that lighter cflrs have lower dircctional<br />
anrl rollovcr stability than hcavy cars. NHTSA's 1988<br />
Technical Evaluation [8] of Congressman Inow Scnatorl<br />
Timothy Wirth's petition further cxplorcs this conccpt,<br />
stilting thtt a number of vehicle size parameters,<br />
espccially wheelbase, ue related to directional stability.<br />
NHTSA stressed that thc high intcrcorrclation of vchiclc<br />
size parameters makes it hard to draw lirm conclusions<br />
on which individual parilnreter is the most important<br />
factor in rollover risk.<br />
During 1988-89 Partyka and Bochly of NHTSA<br />
studicd thc correlation o[ cu weight and fatirlity risk in<br />
various crash modcs [7]. Thcir rcgrcssion cquation for<br />
the rollover fatfllity rilte per 100,000 vehicle years is<br />
fatality rate = 8.01 - .00123 car weight<br />
<strong>The</strong> paper does not address whether this is a "cause<br />
and effect" relationship or a result of thc strong corrclation<br />
of car weight with other vchicle sizc paranrctcrs,<br />
Although the authors do not themselves use the formula<br />
this way, it will yicld a filtillity rate prediction if the<br />
average weight, by modcl ycar, is substitutcd for "car<br />
weight." <strong>The</strong> 1970-82 reduction of curb weight from<br />
3700 to 2700 pounds would be associated with an<br />
766<br />
increase in thc fatality rilte from 3.46 to 4.69, a 36<br />
percent incrctse, nearly identical to thc findings of this<br />
report.<br />
Analysis Method and Datfl Sources<br />
<strong>The</strong> measure of rollover propensity throughout this<br />
report is thc ratio of rollovers to frontul irnplcts with<br />
fixcd objccts. <strong>The</strong> intuitive reasoll l'or thc clroice is that<br />
frontal impacts with fixed ob_jccls conrc closcst to being<br />
a "control" group. <strong>The</strong>y control lbr drivcr and exposure<br />
diffcrences but not for vehicle factors affccting rollover<br />
risk. <strong>The</strong> number of frontal impacts with fixcd objects,<br />
intuitivcly, is proportionul to the frequency at which<br />
aggressive or inattentive driving rcsults in I failure to<br />
kccp the car aimed in the direction ol thc roadway-i.e.,<br />
a potential rollover scenario. <strong>The</strong> greater thc dircctionill<br />
and/or rollover stability of a car, the lbwcr ol' lhcse<br />
potcntiill rollover scenarios becornc actual rollovcrs-irnd<br />
thc lower the ratio of rollovcrs to l'ronttl impacts with<br />
fixed objects.<br />
Thc dilla sources lbr the nnalysis are thc Fttal Accidcnt<br />
Rcporting Sy.stem (FARS) lor calcndar ycars I975-<br />
86 and Texas accident filcs [or l()]2-74 and 1977-83.<br />
FARS data are used to calculilte the ratios of filtcl<br />
rollovers to fatal frontal impacts with fixed objects.<br />
Texas data arc uscd to calculatc ratios for' [priniarily]<br />
nonfiltil] crushes. Thc study relies on Texas data bccausc<br />
thilt is thc only Stats for which NHTSA has files dating<br />
back to the early 1970's. Both files needed adjustmcnrs<br />
for calendar ycar differcnccs and vchicle age effects [5],<br />
pp.93-l0l and 130-140.<br />
Rollover Propensity<br />
Trends, 1970-82<br />
Thc main products of the analysis are year to yctr<br />
trend lines or risk indices f'or rnodel ycars 1970-ti2.<br />
Figurcs l-4 are basod on Texas data (prinrarily nonfttal<br />
crashcs) and indicats the trends in rollover propensity.<br />
Figure I shows thc rollovcr propcnsity inclex by rnodel<br />
year. <strong>The</strong> data points "U" ("unadjustcd" for car size)<br />
show thc actual rltios of rollovers to l'rontal [ixcd obiccl<br />
120 +<br />
12 73 11 15 75 71 78 7e 8o 6l<br />
ffiEL YEAR<br />
Figure 1. Rollover Propensity Index by Model year<br />
(1975'80 Average = 100)
impacts in Texas data, indexed so that the average ratio<br />
for 1975-80 comes out to 100. <strong>The</strong> rollover propensity<br />
index starts at 80-85 in the early 1970's and rises<br />
steadily year after year, especially after 1975, to an all<br />
time high close to 120 in model year 1982. In other<br />
words, rollover propensity increased by almost 50<br />
percent during model years 1970-82-ln l9'10-74, rollover<br />
propcnsity remained fairly stable: the market shift to<br />
smaller car classes was partly offset by the growth of<br />
cars within market classes. <strong>The</strong> real incrcascs bcgan after<br />
1975, thc pcriod of downsizing within car lines as well<br />
as a market shift to smaller car lines.<br />
In Figure 2, rollover propensity is graphed scparately<br />
for -5 market classes of cars; I = lmport, S = Subcompact<br />
(domcstic), C = Compact, M = Midsized, F - Full-sized.<br />
<strong>The</strong> dcpendent variable is LOGR2, the logarithm of the<br />
ratio of rollovers to frontal fixed object impacts t5l, pp.<br />
100-109. Thc logarithm is used because it is more suitable<br />
for statistical rnalyses and for comparing one graph<br />
to another. <strong>The</strong> most obvious phenomenon in Figure 2 is<br />
that smaller cars consistently have higher rollovcr rates.<br />
Full-sized cars are always the best and imports are<br />
almost always the worst.<br />
rcr5t<br />
+0,2<br />
+0, I<br />
0<br />
-0, l<br />
-o,2. r<br />
-0.3<br />
-04<br />
-0. s<br />
l<br />
-0,6 ,c<br />
-0.7 i<br />
-0,E r<br />
-0.9 :<br />
_t.0<br />
C<br />
S<br />
C<br />
S<br />
5<br />
C<br />
-1 .1<br />
-1.2<br />
-t .3 :H<br />
-t,4 r<br />
-l.5<br />
N<br />
l l<br />
_1.6:<br />
-t .1 :F<br />
-1.8<br />
l l<br />
-1,9:<br />
F F F<br />
best<br />
l*------*----*-----*-f970<br />
11 12 73<br />
5C<br />
r<br />
c<br />
t1 15 16 77 18 79 lO 81 8l<br />
ITOEL YEAR<br />
5 s<br />
r l<br />
's<br />
Figure 2. Hollover Propensity by ltlodel Year and Car<br />
Merket Cles$ (LOGHZ; | = lmpod, S = Subcompact,<br />
G = Compact, M = Midsized, F = Full $ized)<br />
It is possible to see the cftccts of size changes within<br />
market classes. Full-sized cars werc downsized in 1977-<br />
79; mid-sized cars in 1975-78; and compact cars in<br />
1980-there are corresponding increascs in rollover<br />
propensity during those years. Domestic subcompacts<br />
became narrower and lighter during 1970-tt2 while<br />
imports became wider, longer and heavier. Figure 2<br />
shows that domestic subcompacts had lower rollover risk<br />
than imports in thc 1970's but lost their advantage in the<br />
1980's.<br />
While Figure I shows a large, steady increase in<br />
aggregate rollover propensity, Figure 2 shows only<br />
moderate increases, if any, within markct classes. As<br />
noted earlier, the size reductions of the 1970-82 period<br />
were achieved by two mechanisms. <strong>The</strong> more important<br />
was the market shift from full-sized cflrs to subcompact<br />
and imported cars, reflected in Figure I but not Figure 2.<br />
5<br />
a<br />
c x<br />
c l r<br />
x<br />
X F F T<br />
c<br />
c<br />
x<br />
x<br />
F<br />
Sectlon 3: Technlca/ Sessjons<br />
Tte effect of downsizing within market classes, reflected<br />
by both figures, is only of sccondary importance and<br />
partially offset by size increases in importcd cars.<br />
A principal task of the analysis is to determine the<br />
extent to which the trends in Figures I and 2 are due to<br />
car size as opposed to othcr factors. <strong>The</strong> task is<br />
accomplished by a log-linear regression of rollover<br />
propensity (LOGR?) by curb weight, track width, wheelbase<br />
and vchicle age. <strong>The</strong> dependent variable in the<br />
regression is the aggregate value of LOGR2 for all cars<br />
belonging to a particular class intcrval of weight, width,<br />
wheelbase and age [5], pp. 109-l18. Driver agc was also<br />
tried as an independent vilriilble and found to have negligible<br />
influence on the regression coefficients of thc other<br />
variablcs. <strong>The</strong> regression coefficients for the model that<br />
best fit the data arc:<br />
INTERCEPT 5.561<br />
TRACK WIDTH -.0962<br />
CURB WEIGHT ..000259<br />
VEHICLE AGE -.0317<br />
R squarcd is .97, a very high correlation. Atthough<br />
wheelbase did not have a significant cffect in this model,<br />
that docs not necessilrily nrean it is unimportant. As<br />
noted eiulier, wheelbase, curb weight and track width are<br />
highly intercorrclated and the regression analysis could<br />
casily confuse their relative effects.<br />
Based on the regression, a new variable<br />
PROPEN2 = LOGR2 + .0962 TRACK WIDTH<br />
+ .002-59 CURB WEICtIT + .0317 VEH AGE<br />
is defined and graphed by model year and markct class<br />
in Figure 3. PROPEN2 measures rollovcr propcnsity<br />
adjustcd for car siz-e. Figures 2 and 3 are graphed to the<br />
samc logarithrnic scale-i.e., vertical distances have the<br />
same meaning in both graphs. It is evident that most of<br />
the variation across market classes and modcl ycars is<br />
explained by thc car size parameters. <strong>The</strong> large variations<br />
across markct classes in Figure 2 shrink to a<br />
nflrrow band in Figure 3, where no single market class is<br />
consistently rtt thc top or bollom ol' the graph.<br />
6.5 :<br />
6-{ :<br />
6.3 :<br />
5,2 i<br />
6.t ;<br />
5.0 :<br />
5.7 :C<br />
5,5 :Il g<br />
5,5 iF F<br />
5,4 i I<br />
5.3 :<br />
5.2 ; 5<br />
3.1 :<br />
5.0:<br />
4.9 :<br />
4,E i<br />
4,1 i<br />
4,6 :<br />
4.5 i<br />
4.t :<br />
CF IC<br />
l t t l f<br />
t t<br />
5<br />
5 5<br />
I<br />
I I T<br />
F C<br />
sF<br />
S<br />
sCF<br />
f<br />
C<br />
t x<br />
s<br />
1l 12, 13 71 75 75 11 78 t9 80 8l<br />
Figure 3. Rollover Propensity by Model Year and Market<br />
Class, Ajusted for Car Siee (PROPEN2; | = lmport,<br />
S = $ubcompact, C = Compact, M = Midsized,<br />
F = Full Sized)<br />
I<br />
d<br />
':<br />
;.i<br />
.ji<br />
'.<br />
':<br />
r.<br />
:i<br />
i<br />
rn<br />
1
1flth Internatlonal Technlcal Conterence on Experlmental Safety Vehicles<br />
Figure 4 shows the rollover propensity index by model<br />
year-adjusled for car size. <strong>The</strong> data points "A"<br />
("adjusted" for car size) are the antilogarithms of the<br />
average values of PROPEN2 across the various market<br />
classes, indexed so thirt the average ratio for 1975-80<br />
comes out to 100. <strong>The</strong> adjusted rollover propensity index<br />
is close to 100 and remains essentially unchanged<br />
throughout 1970-82. <strong>The</strong>re may be a few modcls with<br />
exccptional rollovcr ratcs, but nonc of them has su[[iciently<br />
high sales or extreme rollover rates to pull the<br />
index (average for all cars) away from 100. Rollover<br />
propensity, on the average, is very well correlated with<br />
car size.<br />
rcr5 t 120 +<br />
R :<br />
0 :<br />
L ll5 +<br />
L :<br />
0 :<br />
Y ll0 +<br />
E i<br />
R r A<br />
105 +A<br />
P : A A A<br />
R :<br />
O Im +---------- --------------A<br />
e5|<br />
S +<br />
80+<br />
Delt :<br />
t970 7l t4 75 16 71<br />
i.4OOEL YEAR<br />
l8 79 80 8t<br />
Flgure 4. Hollover Propenslty Index by Model Year,<br />
AdJusted tor Car Size<br />
Rollover Fatality Risk Trends, 1970-82<br />
Figures 5-8 are based on FARS data and indicate the<br />
trends in rollover fatality risk. Figure 5 shows the<br />
rollover fatality risk index by model year, comprising the<br />
net effects of changes in rollover propensity and crashworthiness.<br />
<strong>The</strong> data points "U" ("unadjusted" for car<br />
size) show the actual ratios of fatal rollovers to fatal<br />
frontal impacts with fixed objects, based on FARS data,<br />
indcxcd so that thc avcragc ratio for 1975-ltO comes out<br />
to I00. <strong>The</strong> rollover fatality risk index starts at about 90<br />
in the early 1970's and rises steadily after 197-5 to about<br />
123 in model year 1982 (based on continuing the 1977-<br />
8l trend line through 1982; the actual data point for<br />
1982 is even higher). In other words, rollovcr fatality<br />
risk increased by about 37 percent (123 vs. 90) during<br />
modcl ycars 1970-82. Thc trcnd in rollovcr tatality risk<br />
is quite similar, although not as steep as the trend of<br />
nonfatal rollover propensity (Figure l); in both cases the<br />
rcal incrcases began aftcr 1975, thc pcriod ofdownsizing<br />
within car lines as well as a market shift to smaller car<br />
lincs.<br />
In Figure 6, rollovcr fatality risk is graphcd separately<br />
for the 5 market classes of cars. <strong>The</strong> dependent virriable<br />
is LOGROLL, the logarithm of the ratio of fatal rollovcrs<br />
to fatal frontal impacts with fixcd object tsl, pp.<br />
140-142.It is obvious from Figure 6 that smaller cil.rs<br />
768<br />
rcrlt I<br />
R 130 +<br />
L :<br />
L 125+<br />
0 :<br />
Y :<br />
E 120+<br />
R :<br />
I l0 +<br />
105 +<br />
100 +--<br />
;<br />
:u<br />
90+<br />
85+<br />
o{tr :<br />
------------!-------<br />
, ;i---;i*:;i-li---il-;i-";i--;i*l;--1-";i-li-;i<br />
MOEL YTAR<br />
Flgure 5. Hollover Fetelity Risk Index by llllodel Year<br />
(1975-80 Average = 100)<br />
rcrEt<br />
rl.l :<br />
+1.0 :<br />
+0.9 :<br />
+0,8 r<br />
+0.7:I<br />
+0.6 :<br />
+0.5 :<br />
+0.4 :<br />
+0,3 i[<br />
+0.e:<br />
+0.1:<br />
0 iil<br />
-0.t :<br />
-0.2:<br />
-0,3 iF<br />
-0.4:<br />
-05:<br />
-0.6 :<br />
-0,7 r<br />
-0,8 i<br />
-0.9:<br />
-t.0 :<br />
-t.t :<br />
Dert<br />
I<br />
C<br />
5<br />
t<br />
F<br />
I<br />
C<br />
5<br />
H<br />
F<br />
I<br />
C<br />
s<br />
I<br />
F<br />
l9?0 11 12 13 74 75 16 11 1E 79 80 8l<br />
Figure 6. Rollover Fetality Risk by Model Year and Car<br />
Market Class (LOGROLL; | = lmport, S = Subcompact,<br />
C = Compact, M = Midsized, F = Full Sized)<br />
have higher fatality risk. Consistently, full-sized cars are<br />
at the bottom of the chart and imports at the top.<br />
Figures 2 (nonfatal rollovcr propcnsity) and 6 (fatal<br />
rollovcr propensity) arc graphcd on thc srme loglrithmic<br />
scale. Although the figures look quite sirnilar, it is<br />
readily seen that the range of values in Figure 2 is larger<br />
than in Figure 6. In other words, thc increased rulllover<br />
propcnsity oI small cars rclativc to lilrgc cars tritnslates<br />
to a sorncwhat smallcr incrcase in l'atality risk. That is<br />
because rnany of the additional rollovers of small cars<br />
(in situations whcrc a largc car would havc staycd on the<br />
road or at least rernained upright) are in crashes oI low<br />
scvcrity unlikely to result in fatalilics.<br />
A kcy task of thc analysis is to scparatc the effects of<br />
rollover propensity and crashworthiness in the fatality<br />
index. NHTSA's evalulrtion uses two independent<br />
methods for separating the effects. One is a log-linear<br />
regression of rollover fatality risk (LOGROLL) by curb<br />
weight, track width, wheelbasc and vchiclc agc [-51, pp.<br />
149-167 (actually, scparate regressions arc performed for<br />
ejection and nonejection fatalities). <strong>The</strong> regression<br />
equations are similar to thosc obtaincd from thc Tcxas<br />
U<br />
M s C<br />
c l,l<br />
M C r<br />
c<br />
x<br />
I<br />
c<br />
MF<br />
'<br />
c<br />
F<br />
l,i
data (see above) and indicate little or no change in<br />
crashworthiness after the early 1970's.<br />
<strong>The</strong> other approach is to adjust thc rollovcr fatality<br />
risk index (LOGROLL, based on FARS datfl) for changes<br />
in rollover propensity (LOGRZ, based on Texas data, as<br />
shown in Figure 2). NHTSA's evaluation [5], pp. 169-<br />
183, suggests that<br />
NEWROLLz = LOGROLL - LOGRz/I.9<br />
is the mathematical combination of LOGROLL and<br />
LOGR2 which most closely indicates the trend in overall<br />
fatality risk in rollovers, after controlling for changcs in<br />
rollover propensity-i.e., it is a measure of rollover<br />
crashworthiness. Since car size is thc primc dclcrminant<br />
of rollover propensity, NEWROLL2 also measures rollovcr<br />
latality risk adjusted for car size. NEWROLL2 is<br />
graphcd by modcl year and market class in Figure 7.<br />
Figures 6 and 7 are graphed to the same logarithmic<br />
scale-i.e., vertical distances have thc same nrcuning in<br />
both graphs. Virtually all of the vuiation ircross mtrkct<br />
classcs and model years in Figure 6 is eliminated in<br />
Figure 7. <strong>The</strong> various market classes have nearly<br />
identical crashworthincss valucs (cxccpt toward thc riBht<br />
end of lhe graph where sparse datr rcsult in some<br />
variation).<br />
Frt r<br />
+1.6 :<br />
+r-5:<br />
+1.4 :<br />
+l.3 :<br />
+1.2:<br />
+l.l:<br />
+l.0 :<br />
+0.9:<br />
+0.8 i I<br />
+0.7:I<br />
+0.5 :IcF<br />
+0,5 :<br />
+0-4:<br />
+0,3:<br />
+0.2:<br />
+0.1:<br />
0 i<br />
-0.1:<br />
-0,2:<br />
-0,I :<br />
-0.{ :<br />
-0-5 :<br />
-0,6 i<br />
brrt<br />
CF<br />
Ist{<br />
Of<br />
I5<br />
dl<br />
IF<br />
s<br />
I<br />
Oll<br />
5<br />
s<br />
fi<br />
ICF<br />
t<br />
I<br />
5C<br />
F<br />
n<br />
sCF<br />
I<br />
c<br />
$r<br />
F<br />
Ed<br />
x<br />
F<br />
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5<br />
Hf<br />
t<br />
r 5 t<br />
1970 ll 72 7t 7a 15 16 7l 7A t9 80 81 8E<br />
ffiET YEAR<br />
Figure 7. Hollover Fetality Risk by ModelYear and Market<br />
Cfass, AdJusted for Car Sfue (NEWROLLZ; | = lmport,<br />
S = Subcompact, C = Compact, M = Midsized,<br />
F = Full Sized)<br />
Figure I shows the rollover fatality risk index by model<br />
y et-adj us t e d fo r r o I I ov e r 1t r o p e n s i ty I t: u r si ze . <strong>The</strong> data<br />
points "A" ("adjusted" fbr car size) are the antilogarithms<br />
of the avcrage values of NEWROLL2 across<br />
thc various market classes, indexed so thilt the avcrage<br />
ratio for 1975-80 comes out to 100. This crashworthiness<br />
index is close trl 100 and remains csscntially unchanged<br />
throughout 1970-82. <strong>The</strong> large increrse in rollovcr fatality<br />
risk during 1970-82 (Figurc -5) is not due to a change<br />
in crashworthiness but rollover propcnsity-i.e., car size.<br />
flF<br />
5<br />
f,<br />
R<br />
o L<br />
0<br />
R<br />
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t<br />
lm +<br />
lt5.<br />
il5 +<br />
ll0 +<br />
tos .r<br />
lffi +-----<br />
S +<br />
65+<br />
Section 3: Technlca/ Sessjons<br />
' tu<br />
*rJurr^*<br />
tt tt 7e 80 61 8l<br />
FiEure 8. Hollover Fetelity Risk Index by ModelYear,<br />
AdJusted for Car Size<br />
Estimation of the Fatality Increase<br />
During calcndar ycars 1987-88, tlrcrc wcrc an average<br />
of 4-500 l'atalitic$ per ycilr in prirnrry rollover crashes of<br />
passengcr cars. By 1988. the mix ol' passcnger cars on<br />
the road had size and weight churactcristics similar to<br />
thc modcl ycar 1982 flcct. In olhcr words, thc "baseline"<br />
eslimatc of rollovcr lfltfllities, givcn modcl year 19132 car<br />
sizes rnd lhe calendar yerr 1987-88 driving cnvironmcnt<br />
is 4500 pcr yeir.<br />
How much lower would the nurnber of fatalities hitd<br />
bccn, givcn nrodcl ycar 1970-75 car sizcs in thc calcndar<br />
year 1987-88.driving cnvironmcrtt'l Figurc -5 displays the<br />
rollover tatality risk index by model year. A smooth<br />
curve through thc drtil points yiclds thc following values<br />
[-51, p. 20e:<br />
1970 9t t975 90 t979 103<br />
l97l 90 t976 93 1980 107<br />
t972 89 t977 96 tgtil l 15<br />
t973 88 1978 100 l9rJ2 r23<br />
1974 89<br />
<strong>The</strong> baseline fleet of model year 1982 vehicles, with<br />
a falality risk indcx ol 123, cxpericnccs 4-500 rollover<br />
latalities per yelr. A l'leet of moclel year 1970-7-5<br />
vehiclss. with itrt ilvcragc risk index of 90. would<br />
expericncc 4-500 (90/123) = 3300 rollovcr fatalities,<br />
which is 1200 l'cwer than the baseline rnodel yeal 1982<br />
cars. <strong>The</strong> increase of 1200 fatalitics bctwccn modcl years<br />
1975 and l9fl2 occurrcd dcspitc r rna.ior shil'l froni 2<br />
door cars to 4 door cilrs durirrg the same period.<br />
According to NHTSA's evaluation, the shift from 2 door<br />
to 4 door cars prevents 140 ejection fatalities per ycur<br />
t5l, pp. 218-219. Thus, thc ncl l'fltality increase due to<br />
car size reductions is 1200 + 140 = 1340 fatalitics per<br />
Year.<br />
769<br />
I<br />
|:<br />
r+<br />
di<br />
-a<br />
:<br />
':'j<br />
:<br />
irt<br />
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1 lth lnternatlonal Technlcel Conference on Experimental safety Vehlcles<br />
NHTSA's evaluation attempts to subdivide the net loss<br />
of 1340 lives per yetr according to the various<br />
mechanisms of car size changes tsl, pp. 216-221:<br />
Lives per Year<br />
Saved Lost<br />
Market shift from full-sized<br />
to imported/subcompact cars<br />
Downsizing within domestic car lines<br />
Widcr lracks for some imported cars 230<br />
SUBTOTALS 230<br />
NET LIVES LOST PER YEAR<br />
<strong>The</strong>se individual estimates are derived from the<br />
evaluation's rcgression equations of rollover fatality risk<br />
by curb weight, track width and wheelbase [5], pp. 149-<br />
167. <strong>The</strong>se regression modcls assigned a large influence<br />
to track width and less influcnce to wheelbase and curb<br />
weight. Since the vehicle size parameters are highly<br />
intcrcorrelated, it is possible that the models partly<br />
confused their effects. It so, the benefits of "wider 1220<br />
350<br />
l -570<br />
1340<br />
tracks<br />
for imported cars" would be overstatcd and the losses for<br />
market shift and downsizing likcwise overstated. <strong>The</strong> net<br />
loss of 1340 livcs per year, on thc other hand, is a morc<br />
accurate estimate which does not dcpend on the<br />
rcgrcssion coefficients.<br />
While the methods of this report are appropriate for<br />
estimating the effcct of historictl changes in car size on<br />
rollover fatality risk, it would be inadvisable to use them<br />
to predict what might happen in the future if a sirigle<br />
paramctcr (say, curh weight) is changed while othcrs are<br />
held constant.<br />
References ,<br />
[1] Garrctt, John W. **A Study of Rollover in RuralIf.S.<br />
Automobile Accidents." SAE Paper No. 680772 in<br />
770<br />
Proceedings of 7'welfth Stapp Car Crash Conference.<br />
New York: Socicty ol'Automotive Engineers, 1968.<br />
Griffin, Lindsay l. lll. Prohahility of Overturn in<br />
Sinqle Vehicle Accidents as d Futt(:Iion of RttadT'ype<br />
and Passenger Car Curb Weight, College Station,<br />
TX: Tcxas Transportation Institutc, [l981].<br />
Harwin, E. Anna, and Brewer, Howell K. Analysis of<br />
the Relationshilt hetween Vehicle llollover Stahility<br />
and Rollover Risk Using lhe NII"I'SA CA[tDfile Accident<br />
Datahase. Washington: National Highway<br />
Traffic Safety Administration, to irppear in l9fl9.<br />
Jones, Ian S. "Overturning in Singlc Vehicle Accidents."<br />
Acrident Analysls. London: Planning and<br />
Transport Research and Computation Co., 1973.<br />
Kahanc, Charles J. An Evalualion o.f Door Locks and<br />
Rottf Crush Resisrancti of Passettger Cars-Fedcral<br />
Motor Vehicle Safety Stuntlartls 206 and 216. Rcport<br />
No. DOT HS 807 489. Washington: National Highway<br />
Traffic Safcty Adrninistration, [989].<br />
Malliaris. A. C.: Nicholson, Rohert M.: Hedlund.<br />
Jamcs H.l and Schcincr, Stanley R. Prttltlents in<br />
Crash At,oiduntc antl in Llrash Avoidttnt:e Researth.<br />
SAE Paper No. 830-560. Warrendale, PA: Socicty of<br />
Automo(ive Engineers. t 19831.<br />
Partyka, Susan C., and tsochly, William A. "Passen-<br />
I2l<br />
131<br />
t4l<br />
ts1<br />
l6l<br />
t7l<br />
ger Car Wcight and Injury Severity in Singlc<br />
"<br />
Vehicle Nonrol lovcr Crashes. Tw e lft h I nt e r ndl itt nttl<br />
Technical Cttnference on Experintental Safrty<br />
Vehicles. Washington: National Highway Tratfic<br />
Safety Administration, 1989.<br />
[8] Tcchnical Evaluation of Rulemaking Petition.<br />
Attachmcnt to memorandum by Scott Shadle to<br />
NHTSA Docket No. PRM-MP-004-13. Washington:<br />
National Highway Tral'fic Safety Administration,<br />
August 12, 1988.
s7.o.0r<br />
Wheels Anti-Lock Svstems for<br />
P. Brun<br />
PSA Peugeot - Citroen<br />
Introduction<br />
From the outset, braking system development has<br />
madc a considerable contribution to automobile safety<br />
progress. Thus, successively, with the arrival of<br />
hydraulic control (Peugeot 202 in 1946), front disc<br />
brakes as slandard and high-pressure regulated braking<br />
(Citroen DS in 1954), ventilated discs (-504, in 1968),<br />
then anti-lock brakes (CX in l98l and -50-5 in 1985),<br />
Peugeot and Citroen have never stoppcd developing<br />
active automotive safety.<br />
Today, in this field, the PSA Group brcaks new<br />
ground by offering an anti-lock system on 309, 205, 106<br />
and AX, In fact, until now, only higher-segment<br />
vehicles, for rcasons of cost, could be fittcd with this<br />
equipment. Henccforth, technological developmcnt hns<br />
enabled the fitting on small vehicles of a new twincaptor<br />
specific anti-locking device for a modest price.<br />
Thus PSA offers the greatest number of possibilitics of<br />
acquiring this major safcty system.<br />
Anti.Lock Braking System (ABR)<br />
When a vehicle brakes, the maximum deceleration to<br />
which it can be subject is limitcd by the hws of physics.<br />
It depends on the adhesion betwccn the tyre and the<br />
road. This adhesion is characterised by a factor which<br />
can vary from 0 (no adhcsion) to more than l, and<br />
generally equatcs to 0.9 on a dry tarmac road, 0.6 in<br />
rain, and can drop to 0.1 on icy surfirccs.<br />
As soon as braking starts, a slight sliding of the<br />
wheels on the ground appeilrs. Longitudinal adhcsion is<br />
a function of the wheels sliding on the road and thus<br />
determines the vehicle deceleration capability. According<br />
to the graph bclow, potential decelerrrtion is at its<br />
maximum for a slidc bctween l0 and 30%. However, if<br />
the force applied by the driver on the brake pedal is too<br />
great in relation to the available adhesion, sliding rapidly<br />
increases to reach thc 1007o value, i.e. the wheels lock,<br />
(Figure 1).<br />
This has thrce consequences:<br />
. total loss of vchicle directional control resulting in<br />
the inability to avoid an obstacle or to stay on the<br />
road (the tyre slides on the road surface instead of<br />
turning).<br />
Technical Session 7<br />
Crash Avoidance Research<br />
Chairpcrson: Kare Rumar, Swedcn<br />
Big Series Passenger Cars<br />
Corfi
1lth lntematlonal Technlcal Conference on Experimental Safety Vehicles<br />
signals, the calculator can detcrmine the actual specd of<br />
thc vehicle and the wheels which are close to locking.<br />
<strong>The</strong> ABR Evolution for Big Series Passenger<br />
Cars<br />
Anti-lock brake systems are today widespread in<br />
France, Europc and worldwide. However, their application<br />
is gcncrally limited to the higher market segmcnts.<br />
<strong>The</strong> main reason for this is thc relatively high cost of<br />
these systems (FF.9,600 for a 60-5, FF9,300 for a 405,<br />
FF9,500 for a BX or an XM). This rcnders such systcms<br />
almost incompatible with vchicles of the bottom and<br />
lower middlc scgments.<br />
Thus, in order to increase the availability of this safcty<br />
system, henceforth PSA ottcrs on certain vchiclcs (309<br />
GTI. XS and Srdt. 205 GTI and TurboD, AX GTI, 106<br />
XT and XSi, ...) a new type of anti-lock system: ABR<br />
with twin wheel-speed sensors and twin independent<br />
regulation channels (one per brake circuit). In fact,<br />
whilst usually the speed of cach of the four vchicle<br />
wheels is monitored, here only the two fronl whccl<br />
speeds are mcasured and transmitted to the citlculator.<br />
This new system, devclopcd here by thc BENDIX<br />
Company, is perfcctly suited to thc vchicles already<br />
mentioned, due to its lower cost (notably fewer<br />
components), its lower weight and smallcr volulne<br />
(installation problcms on small vehiclcs). As an example,<br />
in November I991. the twin sensor ABR of'fered as ln<br />
option on the 205 costs FF6,000, whilst thc hasic price<br />
of a 205 GTI I .9L is FF101,300 and thc TurboD<br />
FF85,900. In thc same vein, ABR for the 309 cosls<br />
FF6.200. whilst the 309 GTI costs FF108,900, and the<br />
309 XS 1 .9L cosrs FF8-5.100. Finally, rhe AX GTl, sold<br />
at FF83,100, rcquires an extrfl FF6,000 for ABR.<br />
ABR Twin Sensor System Description<br />
<strong>The</strong> twin sensor ABR system is ptrl of the ldd-on<br />
anti-lock braking system farnily: it is added to a<br />
convcntional braking systcm. <strong>The</strong> system comprises:<br />
. brakc pedal<br />
. vrcuum brake servo<br />
. dual master cylinder with special flnti-lock valves (in<br />
order to withstand back-pressure)<br />
' dual "X" braking circuits<br />
. additional prcssure regulator hydraulic block with<br />
four solcnoid valves<br />
. calculator: separate clcctronic box with 35-way connector<br />
and corrcsponding electricitl wiring. It can be<br />
fitted in the boot (20-5), in the centrill dashboard<br />
inside the vehicle (309) or evcn in the engine compilrtment<br />
(106. AX) which rcquircs very high mechanical<br />
and thcrmal resistance.<br />
'systcm check warning light on the dashboard<br />
. spccial transmission with a hemispherically-cut 48tooth<br />
acoustic crown wheel<br />
. two wheel-speed inductive sensors, mounted on eilch<br />
front whccl pivot (specific). Thcy dctcct variations<br />
in magnetic t'lux cnuscd by the teeth pussing across<br />
the pole. <strong>The</strong>sc variations induce an allcrnating<br />
current (sinustlidal signal) in the coil and tltcir<br />
frequency and amplitude are proportionnl to the<br />
wheel rotational spccd, (Figure 3, Figurc 4).<br />
. two axle-load tlcpcndcnt compensal()rs l() distribute<br />
braking effort to the reilr whccls<br />
. front disc brakcs<br />
. rear disc or drurn brakes, (Figurc 5).<br />
Figure 3. Wheel Speed Sensor<br />
Figure 4. Signal Produced by Wheel Speed Sensor<br />
I Durl rhullEr m$lc. cyllnd..<br />
2 Doprooelon braklng smplllldr<br />
3 computor<br />
4 wheBl epoed mnror<br />
S Solenqird valves<br />
6 Toothed E.r wh6el<br />
7 Hyd'pullc punp<br />
I Indlcetor on Inslrufrenl Pan6l<br />
I conn.ctor lo. dlrgnorlt<br />
Figure 5. Additional 2 Sensor-ABR System<br />
(Anti-Lock System)
Specific Features of the Twin Sensor<br />
Anti-Lock System<br />
. "X" braking circuit requirement. In order to be<br />
able to optimise the front and rcar brakc prcssure<br />
regulation, the twin sensor ABR systern rnust he<br />
installed on a dual "X" braking system (left-front<br />
linked to right-rear, with intcrlinkagc for symmeuy).<br />
A front-rear brake system such as on thc ?05 GTI<br />
1600, would not enable good results to be obtaincd<br />
(no regulatirln at the rear), and for this reason it is<br />
changed to an "X" systcm, with thc ABR option,<br />
(Figure 6).<br />
t tr.rr<br />
2 Dutl mrrt.r cylldl<br />
3 Ds.t br.tlq rlld drHHE<br />
4 Whtrrd r.n.il<br />
5 Hy*.uxc r.gur.ilE rFmtat<br />
6 Crt6utatd<br />
Figure 6. A: Dual"X" Braklng Circuit. B: Dual"X" Braking<br />
Circuit with Additional Dual Sensor ABR<br />
. Special hydraulic assembly. <strong>The</strong> hydraulic assembly<br />
used for the anti-lock system has two sensors<br />
and two regulation channels, conrprising four solenoid<br />
valves. <strong>The</strong> latter modulate braking pressure in<br />
situations outside the optimal whccl sliding band.<br />
<strong>The</strong>se solenoid valves operate in an --all or nothing"<br />
mode, with a reaction time of around 3 to 7 nrs. Two<br />
valves arc fitlcd on cach channcl, thc first bcing an<br />
inlet-exhaust solenoid valve and the second acling as<br />
I restrictive valve for slow pressure variation. Thcrefore,<br />
four basic pressure varirtiun catcgurics lre<br />
available: inlet and release. quick or slow. Frorn this.<br />
by modifying the control time of each solenoid<br />
valve, intermcdiatc pressurc risc and fnll curvss ciln<br />
be obtained, thus ensuring fine pressurc rcgulrtion,<br />
(Figurc 7). Thc group also compriscs:<br />
- an elcctric motor driving two pumps (onc pcr<br />
channcl) to rclurn brakc fluid lowflrds thc milstcr<br />
cylinder aftcr thc prcssurc reduction phases.<br />
two low-pressure reservoirs (one per channcl)<br />
which fill rapidly whcn pressurc drops.<br />
two high-prcssure rescrvoirs (one pcr channel)<br />
limiting pulsltion due ttl pump pressure rise waves.<br />
two anti-pulsation valves (one per channcl) uscd as<br />
a restriction bctween the pump and the milster<br />
cylindcr in ordcr to reduce brake pedal movement<br />
under regulation.<br />
Section 3: Technica/ Sessions<br />
'l *_, 'H 'E<br />
E rgdd<br />
i r.F *""" f"T#,'lff<br />
/ n<br />
lfu- H*<br />
P<br />
Figure 7. Pressure Categories<br />
. More precise regulation logic. Only the speed of<br />
thc two front vchiclc whccls is knowrr. This rcndcrs<br />
the all-irnportilnt dclcnnining of absolutc vchiclc<br />
speed in relulion to lhc ground nruch more delicalc.<br />
Thc prublcrn is furlhcr incrcascd by thc facl tlrut<br />
these whecls urc nrotoriscd. notltrly thc difficulty of<br />
interprcling whcel-spin and regaining adhesion. Due<br />
to lhis, additional algorithrns arc rcquired in lhc<br />
ABR regulation logic and this has led to a far morc<br />
complcx dcvclopmcnt of the systcm.<br />
. Optimising braking effort distribution. In the<br />
absence ol' specd scnsors on lhc rcar whcels, their<br />
locking can only bc avoidcd hy ludicious lront-rcar<br />
distrihution ol hraking cl'l'ort. In l'act, it is rcquircd<br />
that undcr all circunrstrnccs and nolallly undcr all<br />
loads. each rear brake hus:<br />
- a pressure lowcr than thlt requircd to lock thc<br />
wheel.<br />
- a prcssure as high as possible in order to obtain<br />
bcst hcncfit oI ilvirilrrblc adhcsion und lo lrirvc lhc<br />
shortest stopping distlnces.<br />
In order to achievc lhese high-level pcrftrrrnilnces,<br />
relating as lar as possihlc to those ol'l l'our-scnsor<br />
systcrl). a high-pcrl-onniulcc brtking distribution<br />
sysl0ln hus bccn itdoptcd; lwo ilxlc-loud dcpcndcnt<br />
corlrl)cnsiltors (onc ul)slrci[n of clcrh rcar brlkc on<br />
thc dual "X" circuit). 'l'lris crtittrh:s lhc systcrll to<br />
opcrillc its closc rts prtssiblc undcrrlsillh thc idcal<br />
pressurc distrihution curve, (Figurc tt).<br />
(l): Hrd cm (wleltCl<br />
(tlr Eixirr ilE m l$d 6fifflEdr0<br />
A: Utlr lsJ (l Fdi)<br />
8: Mmun hod<br />
Figure L Braking Distribution<br />
i<br />
:<br />
I<br />
'i<br />
- l<br />
:t<br />
I
13t1, lntemetlonel Technlcel Conference on Experlmental Sefety Vehlcles<br />
Load compcnsation control is in fact highly<br />
recommendcd for light vehicles which are pflrticularly<br />
sensitive to mas$ variations ovcr thc rcar axlc,<br />
and for short wheel-base vehicles which are sensitivc<br />
to mass transfers towards thc front undcr braking.<br />
<strong>The</strong> Twin Sensor ABR System Calculator<br />
and Safety<br />
For operational safcty reasons, the numerical<br />
calculator designcd by BENDIX for this ABR has two<br />
distinct micro- proccssors:<br />
. a main l6-bit Intcl 8096 main processor which:<br />
- executes the solcnoid valve software programme<br />
- carries out fault detection: sensors, solcnoid valves,<br />
pump motor, relays, loom<br />
- controls self-diagnosis md storcs fault codes in<br />
non-volatile mcmory.<br />
. a monitoring 8-bit Motorola 680-5 proccssor which:<br />
- calculates the coherencc of thc spccd sensors<br />
- checks the cohcrcncc of thc solenoid valve controls<br />
performed by lhc 8096<br />
' dialogues with the 8096, (Figure 9).<br />
BEHDIX TWIN 5EN5OR5<br />
Figure 9. Electronic Calculator<br />
mnl4 llgfrr<br />
- conlEl<br />
| ,o,t.,<br />
J connectlon<br />
In the event of disagrccment between the two microprocessors.<br />
thc safcty rclay is activated and cirnccls<br />
the ABR function without modifying the conventional<br />
braking system and thc ABR warnittg light is<br />
illuminated on the dlrshborrd. In certain cases, with<br />
very localised faults in the ABR system, the calculator<br />
can adapt itsclf and continue to operiltc in<br />
"degraded"<br />
mode.<br />
ABR Self-Diagnostics<br />
To help maintcnance and trouble-shooting, thc calculator<br />
is fitted wittr a self-diagnostic dcvicc, cnabling the<br />
detection by a scrics of lutrtinous flashes of the typo of<br />
defect present in mcntory. It opcrates as follows:<br />
. each elemcnt is linkcd to a number (e.g. for thc<br />
front-left inlet-exhaust solenoid valvc: code 44):<br />
' when the fault appcflrs, the code is memorised in the<br />
calculator's non-volatile memory (codc snvcd in thc<br />
event of lhe box bcing removed from the vehiclc);<br />
774<br />
. this code remains in memory even if the fault disnppeirrs;<br />
. this code can be sent on request either by a serial<br />
conncction (at thc tactory), or by luntinous flashes<br />
by connecting a bulb to the dirgnostic sockel, or by<br />
using a spccial dcvice, thc TAD 99 (Self-diagnostic<br />
Tcstcr), which automatically carries out the diagnostic<br />
request and cleiuly registers the fault code;<br />
. after repair, it is necessary to wipe this code from<br />
the calculator mcmory by earthing the diagnostic<br />
lead for l0 seconds or by pressing the "erase"<br />
bullon<br />
on the TAD 99, (Figure l0).<br />
1 c -<br />
2 FrlhrHod|. dShY<br />
3 E.rEhg ol th contdld rfiil tF<br />
4 Eruslon ol the comPul/r m6mory<br />
5 dmpult/r Interq!ilon<br />
6 csmcllng plugrothe ccmpul.r<br />
7 El*tdq Pow.r tupplt<br />
Figure 10. Auto'Diagnosis Tester TAD 99<br />
<strong>The</strong> Twin Sensor ABR Development<br />
Thc dcvclopment ilnd manufacturc o[ anti-lock systems<br />
such as thc twin sensor ABR fittcd to PSA vchicles<br />
are entrusted to outsidc suppliers such as BENDIX, in<br />
the present exrmplc. In I'act, the relative complexity of<br />
the prtlducl rnd thc high investmenl cosls-notitbly in<br />
terlns of testing-makc this flctivity difficult to integrate<br />
wilhin lhc slructure of a liuge gencral manufaclurer such<br />
as FSA.<br />
Thus, for each new model study. lhe supplicr has for<br />
several monlhs a sulficicnt supply of trtechanically rcprc-<br />
$entative vehiclcs to bc a[rlc to ada;tt his anti-lock<br />
$ystem. After fitting out thcsc vehicles, they are taken<br />
for the entire wintcr for tcsting on lhe large frozen llkes<br />
in Sweden. In a snrall town neilr the Arctic Circlc, onc<br />
can find Ihc majority of anti-lock manuftclurcrs. Thcrc,<br />
they have many low- adhesion tcst tracks on which it is<br />
possible to travel at 150 kph and lo brake hard in almost<br />
complctc safety. Under these condilions, which cannot be<br />
reproduced in Franco, thc dclicfltc dcvcloptnent of the<br />
anti-lock systcm sol'tware programme for each vchiclc is<br />
perfected.<br />
Validating the Twin Sensor ABR System<br />
flt PSA<br />
On receipt of the new ABR system, PSA validates it<br />
by a test progrilmme which lakcs place:
. in Sweden, on the frozen lakcs used by the suppliers,<br />
. in France, on special tracks which are particularly<br />
valid for high and average adhesion.<br />
<strong>The</strong> PSA validation tests are as follows (in each<br />
situation there is maximum braking with ABR intervention):<br />
. Directional control. Vehiclc directional control in the<br />
following cases:<br />
- braking whilst avoiding an obstacle<br />
- braking whilst changing one or two lanes<br />
- braking on skid pans<br />
- braking in a straight line and on entering bends<br />
- braking on leaving bends<br />
. Vehicle stability. Corrcct rear axle tracking (same<br />
conditions as directional control).<br />
' Stopping distances. Measurements in relation to<br />
initial speed and adhesion.<br />
'Left-right asymmetric adhesion (or mu-split). This<br />
occurs when two wheels on the same side have high<br />
adhesion (tarmac) and the two others have low<br />
adhesion (snow, wet grass on the verge, for<br />
example). In these conditions, braking inevitably<br />
creates an often brutal yawing movement, which<br />
takes the vehicles towards the most adhesive side.<br />
Strong and sharp corrcction of thc steering wheel is<br />
then necessary. In the most critical cases (high<br />
adhesion asymmetry), the vehiclcs spins round. ABR<br />
prevents any locking of the front wheel, notably on<br />
the side with less adhesion (with this twin sensor<br />
system, locking of the rear whccl on low adhesion is<br />
permissible). This enables the tyres to maintain optimal<br />
transversal adhesion and thus the vehicle resists<br />
as fm as possible the turning torque. Furthermore,<br />
ABR can delay the pressure rise in the lnore<br />
adhesive side (momentary partial undcr-braking).<br />
This diminishes the yawing effcct and thc steering<br />
wheel correction can be made by any driver.<br />
. Adhesion transition. This is the srudy, during<br />
straight-line braking, of the passing from high to low<br />
adhesion and vice vcrsa. Pedal hcight variations and<br />
system reaction speed are the particular fields of<br />
analysis.<br />
. Pedal comfort-filtering. Pedal moyemenI in the regulation<br />
phase is unavoidable and must be attenuilted,<br />
but not necessarily suppressed; in fact these arc the<br />
warning signals alerting the driver that he is at the<br />
limit of adhesion. <strong>The</strong> three analysis criteria are:<br />
oscillation, vibration, travel.<br />
. Comfort-operating noise. <strong>The</strong> noise is basically<br />
caused by the pump and solenoid valve operation<br />
and this highlights the importance of selecting the<br />
correct location for the hydraulic block and<br />
acoustically insulating it.<br />
. ABR extreme operating conditions:<br />
- rapid braking release and re-application<br />
- linked over-acceleration and braking<br />
Seetlon 3: Technleal Sesslons<br />
- rebound braking/jumping (instanraneous locking)<br />
- braking ovcr mixed adhesicln surfrces.<br />
All these tcsts are carried out at different speeds, with<br />
the clutch engaged and discngaged, and with varying<br />
lcvels of adhesion.<br />
Dual Sensor and Four Sensor ABR System<br />
Comparison<br />
In order to highlight the effectivcness of thc BENDIX<br />
twin sensor ABR system in the vehicles into which it is<br />
fitted, below is a comparison with a four $cnsor systern,<br />
in accordance with two of the prcviously listcd criteria:<br />
stopping distance and directionill srability.<br />
Two vehicles, A and B, arc used. A is tilted wirh the<br />
BENDIX twin sensor ABR, whilsr B has lr compctiror's<br />
highly reputed four sensor ABR $ystem.<br />
Furthermore, these two vehiclcs are absolulely<br />
identical and tcsted undcr the sarnc conditions:<br />
. idcntical vehicle mass<br />
. identical tyres, sarle wear condition, sf,me inflation<br />
pressurc<br />
. identical braking distribution systems<br />
. idcntical brake pads, with rhe same dcgrce of wear.<br />
Thc vehicle comparison is simultaneous to removc ilny<br />
variations in adhesion.<br />
. Stopping distance comparison. <strong>The</strong> distance required<br />
to come to a complete halt is measurcd, with the<br />
vehicle's ABR system in permanent usc (therefore<br />
with maximurn pedal pressurc). Cornparison is made<br />
for varying lcvcls of adhcsion and at different<br />
speeds. Each result is taken from thc average of l0<br />
tests, 5 of which were completcd with the clutch<br />
engaged, (Figure ll).<br />
+A*<br />
25<br />
20<br />
t5<br />
0<br />
-5<br />
.10<br />
-t5<br />
-20<br />
-25<br />
-Ar<br />
ffi ffi<br />
H<br />
ry<br />
E<br />
ffi<br />
Y f<br />
ffi<br />
f i f f<br />
lro+tffi<br />
ffi fEl VIffiffi<br />
Figure 11. Stopping Distance Variatlons: Twin Sensors<br />
ABR BENDIX Compared with the Four Sensors<br />
Benchmark (Veticle in Charge)<br />
It was noted, in accordance with our expectations,<br />
that on averaBe the twirr scnsor ABR systcrn offers<br />
a slightly lower performrnce than a four sensor<br />
sysfem. Howcver, the measured averagc increase in<br />
stopping distance-about l07o*remains wcll below<br />
thc 30 to 40Vo measurcd between braking with<br />
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13th Internattonet Technlcal conference on Experlmentel sefety vehlcles<br />
locked wheels and braking with four scnsor ABR' In<br />
thc specific example of high adhesion, the pcrformancc<br />
of both systems is comparable, as the<br />
stopping distance increase is only 37o, whilst with<br />
locked wheels + 20Vo wali measurcd'<br />
. Low adhesion dircctional stability comparison. <strong>The</strong><br />
vehicle is in a circle of radius 250m, with a solid ice<br />
surface. Vmax is the maximum speed around this<br />
curve without steering wheel correction. <strong>The</strong> initial<br />
test speed is takcn as 0.9 x Vmax and braking to<br />
come to a halt is carried out in lhe curve, clutch<br />
engaged, without steering wheel corrcction. <strong>The</strong><br />
stopping distances and dcviation at the cnd of<br />
braking are measured, (Figure 12, Figure l3)'<br />
Figure 12. operating Iththod<br />
Tfirorrtlc |ftFdoty<br />
ot thc end ol broking<br />
-n)<br />
lr mo* (nhm) I 2 ffi AIR EEHN(<br />
Figure 13. Directional Stability on Natural Low Adhesion<br />
Surfacs: Stopping Distancse and Comparative Curve<br />
Deviation<br />
<strong>The</strong> rcsults show that the variation in stopping<br />
distances corrclate with previous tests. <strong>The</strong> deviation<br />
becomes greillcr with the twin scnsor ABR system, but<br />
remains within acceptahle limits, as it is low, bearing in<br />
mintl the low levels of adhcsion. Furlhcrmorc' it is<br />
incontestably superior to that (hypothetical) that would<br />
be measured with locked wheels hecause, in this case'<br />
the vehicle woulcl spin around at thc stilrt of hraking'<br />
<strong>The</strong> notions of deviation and stopping distirnce would<br />
therefore be academic'<br />
Furthermore, to enable comparisons to be nrade, the<br />
test describcd here was carried out without steering<br />
wheel correction. Howcver' ilny driver could of course<br />
reduce deviation by taking appropriate correclivc action'<br />
ABR: Pratical Driving Recommendations<br />
<strong>The</strong> anti-lock wheel systcm thus enables optimum<br />
automatic use of available adhesion. But it is not ablc to<br />
correct for a stylc of driving which is not ilpproprlilte to<br />
traffic and road conditions. It is not a licence for<br />
imprudent driving. In particular, stopping distances must<br />
still be considered as wcll the speed at which bcnds are<br />
neSotiatcd, because these are governed by unchangcable<br />
physicll laws. Furthcl'more, lhc serviceablc contlition of<br />
thc vehicle rctnains of printary importance: shock<br />
absorbers, brakes, tYres.<br />
ln the evcnt of heavY braking:<br />
. On a slippery surfacc, as soon as one wheel has a<br />
tcndency to lock. the ABR is activatcd' <strong>The</strong>n<br />
maximum brakc pressure should be irpplied without<br />
pumping. For the driver' this is fclt by hrakc pedal<br />
oscillations and heavy clicking noiscs (solenoid<br />
valvc actuation) and some shudders in vehiclc<br />
decelcration, corresponding lo thc succcssivc brakc<br />
- pressure riscs and falls during thc ABR regulntion<br />
phase.<br />
' On a dry surface, it is also possible to hear tyre<br />
squeal. which ctlrresponds tr.: optimum whcel sliding<br />
(govcrned by thc ABR systcm) representing the best<br />
possible use of the available adhesion.<br />
Conclusion<br />
<strong>The</strong> advantagc of the ABR twin sensor systcnr' proven<br />
and fittcd on small vclticlcs irt PEUGEOT and<br />
CITROEN, clcarly shows through thc virrious tests'<br />
Without equalling thill of a systcrl wi(h four sensor<br />
rcfcrencc poinls, it does achicvc a vcry high levcl of<br />
perfornrance, under any tyrc/road adhesion conditions. lts<br />
modcst price and its excellcttt price/pcrforntttrce ratio<br />
have thus become major advantages which today cnable<br />
the PSA Group to offcr to the widest clientelc a truc<br />
anti-lock system, a fundamcntal cletnent in autotnobile<br />
safety.<br />
Acknowledgment<br />
We express our thatlks to: BENDIX Francc for<br />
thcir assistancc in producing this articlc.
Improvements in Active Safety by Innovation for Automatic<br />
Stability Control Systems<br />
Dr.-Ing. Heinz Leffler<br />
BMW AG<br />
Abstract<br />
Additionally to thc alrcady available ASC and ASC+T<br />
of the BMW top models newly designcd stflbility conrrol<br />
systems will bccome introduced in the 3-series and 5series<br />
BMW cars. All these systems arc applicable on<br />
mcchanic and automatic gcarbox-equipped cars. Whcreas<br />
ASC, available at BMW sincc '87, is a pure enginecontrol<br />
system, where rcduction of engine torque is used<br />
to avoid stability-critical situations on low-p road<br />
surfaccs, the htest Automatic Stability Control Systems<br />
of BMW (ASC+T) additionally apply active braking to<br />
the driven whcels. <strong>The</strong> engine control of BMW's ASCsystems<br />
is based on a selected interfacc structure of<br />
cnginc mflnagement and transmission control units.<br />
Throttlc conlrol as well as active braking is realized<br />
diffcrently depending on the respective modcl range.<br />
Whcreas the BMW 7-50i and 850i use bifluid hydrtulic<br />
units in add-on technique for ASC, ABS-integratcd<br />
hydraulics in opcn or semi-open versions will bc apptied<br />
to thc other types of the BMW model range. <strong>The</strong> ncwly<br />
designcd ABS-integrated ASC-systems form the basis for<br />
further increased penctration of the car market with<br />
stability control systems. <strong>The</strong> different systcms described<br />
in this papcr show remarkable improvcments in vehicle<br />
stability as well as in traction capability during critical<br />
driving situations. Pcrformance data and statistical<br />
analysis of tcst results obtained with ASC-equipped cars<br />
prove, that the Automatic Stability Control Systems<br />
contribute significantly to improve activc safcty.<br />
Introduction<br />
Safcty control systems suffer from lhe matter of fact,<br />
that thcir prcsence in nearly all cascs is not recogrriztblc<br />
insidc or outside the car. To convince a custorner ol' thc<br />
advantages cf a safety systcm, thus requires a wellestablished<br />
argumentation or customer's experiencc<br />
having mastered a critical situation only becausc of the<br />
safcty control system in his car.<br />
Among other safety control systems Anti-Lock Braking<br />
Systems (ABS) and-as a quasi invcrsion of the<br />
ABS-Automatic Stability Control Systems ASC, contribute<br />
Brcatly to improve active safety of passcnger cars<br />
as well as of commercial vehicles and buscs. BMW as a<br />
manufacturer of passengcr cars have rewarded the safety<br />
consciousness of their cuslomers and are equipping all<br />
their modcls with ABS as a standard.<br />
Automatic Stability Control Systems ASC have been<br />
introduced in 1987 for some top-of-the-rilnge cars and<br />
Seetlon 3: Technlcal Sesslons<br />
meet just nowadrys the phase of integration and application<br />
from top to hottonl rangc of thc procluction line.<br />
As a rcsult of the enginecring work linked with rhis<br />
introduction-phasc, BMW have designed-togclhcr with<br />
their suppliers Bosch lrnd Teves-two ABS-intcgriltcd<br />
stahility- and traction-control systems which will be<br />
introduced in thc 325iand 52-5iat the begirrrring of 1992.<br />
<strong>The</strong> integration of ths AS(I-controller and thc ASChydraulics<br />
in the existing ABS-systenr forms a vcry<br />
space- rnd weight-optimiz-ed design, which will become<br />
thc basis for furthcr futurc cnginccring work around<br />
brake and stability-control systcnrs.<br />
ASC-Systenrs at BMW<br />
Two catcgorics 0f ASC-systems rre available flt BMW<br />
nowadays. Purc stability-contt'ol systents which infl ucnce<br />
engine only, were introduccd in 1987. To irnprovc traction<br />
espcciltlly on friction-splittcd surfaccs, the introduction<br />
of a differerrtial brake eft'ect with the ASC+T in<br />
1989 led to a rcmarkablc progress IlJ. Furthcr intcgration<br />
of hydraulics and clcctronics resulted in innovltive<br />
ASC-systems, wilh il cornrnon hardwarc whiclr simultaneously<br />
is rtpplicd for ABS- and ASC-control.<br />
Figurc I gives a general vicw of the control circuits<br />
applicd to the differcnt systcms ts well as a rclation to<br />
the adjace nt BMW models. <strong>The</strong> rate of intcgration of the<br />
hydraulics and the electronics can also bc picked-up.<br />
BMW Model<br />
Flanoe<br />
ASC ASC+T<br />
gA.rul.<br />
7ffi4.7ffi4.ffi 7stl. M/l 95ff1 wl<br />
Throttle x (EML) X (EML) x(ADSz x (ADSz<br />
lonition/ x x x<br />
lnigctlon Cutorrt<br />
lgnition Timing x x x x<br />
Difl616ntial<br />
Brak6 x x x<br />
Add-On<br />
ASC-Hydraulics<br />
AgS-lnt6orated<br />
x ASC-Hydiauhcs x<br />
ABS-lntsgrat€d<br />
ASC-Elqct@nics x x x x<br />
EML: Electronicallv Controll6d Thronl6<br />
AOSZ: Eldclro-MechaniHl ThrottlB Actuator<br />
Figure 1. ASC/ASC+T, Comparison ol Control Circuits<br />
x<br />
<strong>The</strong> ASC communicates with the engine and transmission<br />
manilgcnrcnt to reduce exccssive whccl slip at<br />
the drivcn whccls, slilrting or driving on stirbility-cl-itical<br />
rold surfaces. <strong>The</strong> control circuits to be used for this<br />
purpose are the throttle contlol, the injection- and<br />
ignilion-cutout nnd the ignition-tirning adjustment.<br />
Throttlc control takes place by intcrlacing with the<br />
contlol unit of an clcctronical accelerator. This<br />
,i<br />
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lSth Internatlonal Technlcal Conlerence on Experimental gelety Vehlcles<br />
communication link provides the reduction of whecl slip<br />
also during situations in which thc driver shifts down in<br />
low gear or releases the accelerator pedal on low-friction<br />
roads, whereby engine drag may bc sufficient for causing<br />
brake slip at the driven wheels.<br />
Via an intcrface to thc electronics of the automatic<br />
gearbox ASC influences the gear-shifting logic in such<br />
a manner, that unnecessary Sear changing during ASCcontrol<br />
is stopped or modifications of the geil-chanBing<br />
program arc initiated to allow earlier shifting in higher<br />
gear.<br />
<strong>The</strong> first ASC+T-T is the abbreviation for tractionused<br />
a bi-fluid add-on ASC-hydraulic unit with intc'<br />
grated piston-type nitrogen accumulator to produce a<br />
differential brake effcct at the driven wheels, which<br />
stops exccssive wheel slip at one or both wheels of the<br />
drive axle, starting or driving on adhcsion-critical road<br />
surfaces. Bcsides brake control, throltlc control as wcll<br />
as ignition timing arc available ils control circuits on the<br />
ASC+T actually uscd on BMW's 750i and 8-50i- Ignition<br />
and injection cutout in this system arc replaced by the<br />
fast brakc-control circuit.<br />
In contrast to the add-on ASC+T of thc BMW 750i'<br />
850i the ASC+T of the BMW 325i as well as of the 525i<br />
are fully ABS-intcgrated systems, where not only the<br />
electronics but also thc hydraulics arc commonly used<br />
for ABS- and ASC-purposcs. Both systcms are providcd<br />
with control circuits for brake, throttle, ignition/<br />
injection-cutout and ignition timing. <strong>The</strong> throttlc position<br />
during ASC-control is modified via an electric motor<br />
with integratcd gear ratio (ADS2), to rcduce the lhrottle<br />
against driver's demand. For this purposc the throttlc is<br />
equipped with a decouPling unit.<br />
Thc ASC+T of thc BMW 325i is based on the TEVES<br />
ABS MKIV with an open hydraulic systcm, whereas the<br />
system forcsccn for the BMW 525i uses the ASCextendcd<br />
Bosch ABS2E with semi-open hydraulics<br />
during ASC-mode and closed hydraulic system during<br />
ABS-mode. All ASC-systems in use at BMW are applicablc<br />
on manual gcarbox-equipped cars as well as on<br />
automatic gearbox one's.<br />
ABS-Integrated ASC+T<br />
Systern Diagram<br />
<strong>The</strong> ASC+T of the BMW 325i is based on TEVES'<br />
ABS MKIV which was cxtended hydraulically to allow<br />
individual wheel braking at the rear axle anrl to provide<br />
active braking to reduce excessive drive slip' In case of<br />
the 325i each modulator consists of a pair of 2/2-stagc<br />
valves, to allow different pressure steps during ABS- or<br />
ASC-control. In Figure 2 the basic layout of the ASC+T<br />
of the 325i is presented.<br />
To gencrate a very fast brake application especially<br />
during the first ASC-control cycle a spring-loaded piston<br />
accumulator is integrated in thc system. Systent pressurc<br />
is controllcd between ?0 bar and II0 bar viit an elcctric<br />
pressure switch. To isolatc the piston accumulator from<br />
778 l<br />
Figure 2. ASC+T of BMW 325i (TEVES Sy$tem)<br />
the basic brakc system a normally closcd 2/2-stage valve<br />
is incorporated in the accumulator. Separation of milster<br />
cylinder and rear axle brakc circuit during ASC-control<br />
is achieved by rnothcr-nortnally opcned-2/2-stitgc<br />
valve. Parallcl to the litttcr valve a prcssure-relieve valve<br />
is requircd, allowing ntaxitnum prcssure of 140 bar'<br />
Bccause of thc open hydraulics being used by the<br />
TEVES systcnl, certain precautions wcre required to<br />
achievc at least thc same sirfety stilndard and pedal<br />
comfort as with commonly uscd closed hydraulic-ABS<br />
systems. By a sophisticated blukc pedal trlvel logic-a<br />
travel sensor is incorporatcd in the vflcuum booster-this<br />
ambitious goal was achievcd. Additionally the function<br />
of the electric-driven pump is monitorcd by a spccd<br />
sensor fixed at the electric motor. Wheel-speed sensing<br />
takes placc via convcntional inductive speed pickups<br />
dctecting specd informltion of toothed wheels-<br />
Thc ASC-control of cngine and transntission is<br />
achieved via an interfilce structurc to the digitill motor<br />
electronics DME and the control unit of thc automatic<br />
gcarbox EGS. Throttle control is clrricd out by a<br />
scparate electric-driven lhrottle aclualor ADS2' which<br />
with rr bowden wire connected to thc throttle can rcduce<br />
the throttlc position with its dccoupling mechanism<br />
against drivcr's demand.<br />
Figurc 3 shows the basic layout of the Bosch system<br />
used on the BMW -525i. Similar to the syslcm of the 325i<br />
the ASC+T is bitscd on thc ABS. ln casc of the Bosch<br />
system the hydraulic unit is of a slightly different dcsign<br />
comparcd to the non-ASC nrodcl. <strong>The</strong> modulirtors of the<br />
ASC+T cll'the 525i are of thc 3/3-stage typc. Like the<br />
32.5i the numbcr of modulators of the 525i hydraulic unit<br />
had to be cxtended by one, to allow individuul wheel<br />
braking at the rear lxle.<br />
A 3/2-stage solenoid was introduced in the line<br />
betwccn milster cylinder's rcar-axle conncction and rearaxle<br />
input of the hydraulic unit. In the casc of ASCfunction<br />
this solenoid is energizcd and interrupts the<br />
rcar-axle linc to the mastcr cylindcr. In the cncrgiz.cd<br />
position the 3/Z-stage solcnoid connects the pressurc<br />
circuit via I prcssure-relief valve with the reservoir.<br />
Rclief pressure is nominally ttO blrs.
Flgure 3. A$C+T of Bkl\tY 525i (Bosch System)<br />
In the suction line between pump and reservoir a<br />
hydraulically actuatcd 2/?-stage valve is introduced. lts<br />
purpose is to intcrrupt the connection betwcen open<br />
reservoir and closed hydraulic circuit during normal<br />
braking or ABS-application.<br />
<strong>The</strong> engine control during ASC-mode operates basically<br />
like with thc 325i's system: interfaces exist to the<br />
control units of engine and transmission, the throttle is<br />
controlled with the same electric actuator ADSZ.<br />
Electronic' s Block Diagram<br />
<strong>The</strong> block diagrams of both system's electronics (Fig.<br />
4, 5) indicate that the throttle actuator (ADS2) is<br />
controlled by the ABS/ASC-control unit. Whereas the<br />
TEVES-systcm uses 3 identical 87 C 54 controllcrs to<br />
implement the control and safety logic of ABS and ASC<br />
as well as for thc ADS2 throttle actuator. the Bosch<br />
system prefers two C 196 KR micro controllcrs for ABS/<br />
ASC-function and a 68 HC I I for the ADSZ.<br />
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Figure 4. Blod< Dlagram of ABS/A$C+T-Gontrol Unit for<br />
BMW 32sr<br />
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<strong>The</strong> word length in the TEVES-system is 8 bit, Bosch<br />
uses l6 bit for ABS/ASC-logic and 8 bit for the ADSZcontrol.<br />
Practical differences from thc word-length<br />
limited rescrlution of the micro-controllcrs cannot occur,<br />
bccause internal arithmetic operation in thc TEVES<br />
controller allow the same resolution as the Bosch control<br />
unit.<br />
Both electronics serve ISO diagnosis, so that permanent<br />
or sporadic system failures can be detected easily.<br />
Svstem failures of the ABS or the ASC+T arc indicated<br />
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Flgure 5. Blod< Diagram of ABS/ASC+T-Control<br />
BMW 525i<br />
Unit lor<br />
to the driver by two different warning lamps. System<br />
tailure is inrlicrted by a permanently lightcd lanrp of thc<br />
adjacent system, ASC-control is indicated with a 3 Hz<br />
flashing of thc ASc-lamp.<br />
To gencrale l position control circuit for the throttle,<br />
a throttle potentionre(er serves the actual throttlc rngle<br />
to the electronic control unit. Engine speerl is considcred<br />
as well.<br />
ASC+T Controller BMW 325i1525i<br />
ASC-Controllcrs sr-r frr available at BMW either werc<br />
developed for purc cngine control (ASC) or for cornhined<br />
engine and brakc control system ASC+T, the latter<br />
based on bifluid plunger hydraulics. Thc ASC+T systems<br />
presentcd hcrc are fully ABS-integrated systems, conccrning<br />
clcctronics as well as hydraulics. <strong>The</strong>rcfore rtcw<br />
logic structures had to be designcd to optimize the<br />
respective car and control systcm on each other.<br />
Outstanding high-lights of the new ASCI+T-logic for<br />
the BMW 52-5i are new ltlgorithms for cornering, variable<br />
slip thrcsholds considcring tlifferent grldients and<br />
an increased conlrol I'rcqucncy. <strong>The</strong> dcgree of stability<br />
during corncring could be determined rnore preciscly and<br />
hill-climbing ability wrs improved also by selective<br />
trcatnlcnt of individual whecl bchaviour driving on a<br />
gradient or in hair-pirr bcncls.<br />
By consideration of the cnginc map, depending on the<br />
respective situation, digressivc or progrcssivc routincs<br />
for throttle-control will be applied. As a rcsult ot lhis<br />
saw-tooth shrpcd cngine spced behaviour during ASCcontrol<br />
is prcvcrrted and the utilization of adhesion is<br />
increased.<br />
Figure 6 shows a control cycle of the ASC+T of the<br />
BMW 525i on a split-p tost trilck. Split-p was between<br />
ice and asphalt. Throttlc demand was ncitrly 1007o, whcn<br />
the ASC+T by suitably adapted activation of thc diffcrent<br />
control circuits for engine and brakc assistcd the<br />
driver in starting on this critical road surface. Average<br />
brake pressure wrs approxinrately 30 bars at the brakc of<br />
the low-p wheel.<br />
<strong>The</strong> logic for ASC+T of the BMW 325i has features<br />
similar to thosc of the BMW 525i. trut is realized ditferenily<br />
of course. Aput fronr logic-cornbinations l'or the<br />
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Figure e. Jontrol Cycle on p-Split, ,"* UrU,<br />
dctcction of cornering and hill-climbing spccial precautions<br />
for the excessive power of the BMW 325i had<br />
to be taken into account in order to guarantee control<br />
comfort and high utilization of adhesion. Conlinuous<br />
transitions betwccn Select-High and Sclcct-Low control<br />
are possible by selective treatment of thc control deviation<br />
of the tractive whccls. <strong>The</strong> speed of throttlc control<br />
is adapted automatically to the momentary slip of the<br />
driven wheels.<br />
As an example of a control cycle Figure 7 shows the<br />
relevant control circuits of the ASC+T, when starting thc<br />
BMW 32-5i on a split-p road very similar to the one used<br />
in Figure 6. <strong>The</strong> throttlc actuation wrs fastcr than for the<br />
BMW 525i, resulting in slightly longer injcction/ignitioncutout.<br />
Brake control-pressure with approximately 35<br />
bars also is slightly higher with very small variations<br />
about the mean value.<br />
Figure z. control Cycle on p-Split, ,tW rrri<br />
3 Thsrsr<br />
Both examples of ASC+T control cycles on p-splitted<br />
roads indicate, that indcpcndently of the tliffcrcnt basic<br />
ASC+T-systcms and vehicle concepts a similar system<br />
performance is achieved. Thc vehicle dynamics on<br />
diftcrent test tracks being prcsented in the following part<br />
will underline this statement.<br />
Stochastic Driving Tests<br />
Comparing cars with and without ASC, very soon<br />
leads to the conclusion, that Faction and stability are<br />
remarkably improved, especially when driving on lowadhesion<br />
surfaces. But not only these vcry obvious<br />
singularities prove thc benefits of modern brakc and<br />
drive-slip control systems: also instationary driving tests<br />
show, that ASC+T can reduce drivcr's physiological<br />
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stress very significantly and improve the nctive safety of<br />
the car/driver systcm.<br />
Tests on four diflcrcnt te.st tracks wcrc carried out, to<br />
find out, how the bencfits of ASC can bc quflnlil'icd.<br />
Thcsc tracks were<br />
' a handling course with bends of different radii,<br />
. a typical part of lhis course stimulating ASC-control<br />
with bends of changing direction,<br />
. a sinusoidal course,<br />
. anothcr handling coursc with llends of grettcr radii<br />
allowing maximum spccds up to 180 kph.<br />
From cilrlicr investigatiorr work [2] it was known that<br />
thc spcctral analysis irnd statistical evaluttion of<br />
instationary driving manocuvres was an irpproprintc<br />
techniquc to compare the influcnce of ASC on road holding<br />
and on driver's cl'lort contnrlling a cnr. In this cilse<br />
the dcscription of the inlcrcsting vehicle motions in<br />
terms of cffcctive values wits considered. As a rcsult of<br />
this Figure I to l0 show by alr assessmcnl of yaw rate<br />
and steering anglc, mcasured at thc stccring wheel, to<br />
what extent ASC+T influences vehiclc dynamics.<br />
Comparing the BMW -12-5i on wet and dry asphalt<br />
handling course, it can bc seen, that whcn switching off<br />
tho ASC the driver has to gcncrate up to 13.3% higlrcr<br />
steering cffort to control il car thal show"^ an incrcitsc in<br />
yaw of 25.8o1'. <strong>The</strong> respcclivc ligures on dry tsphalt are<br />
lower: thc yaw rate incrcrscs lty 25% only, whcrcas<br />
steering rcquircs 8.07o highcr steering angles (Fig. 8).<br />
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Figure L Steering Eflort and Yaw Rate, BMW 325i,<br />
Handling Course<br />
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On a special section of a test track used with the<br />
BMW 525i with anrl without ASCI. stecring cl'l'ort<br />
increase-c betwccn 7 -60/o (dry road) and l9.57rr (wet<br />
road) driving wilhout ASC (Fig. 9). <strong>The</strong> adjacent yaw<br />
rate increase ilmounts between 5.37o (dry) and 8.09o<br />
(wet). <strong>The</strong> section considcrecl for this invcstigalion<br />
consists of a bcnd with progressively dccrcasing radius,<br />
two bends anti-clockwise and a gradicnt with a hair-pin<br />
bend. Both rcsults prove thilt with ASC+T a rernarkable<br />
rcduction of driver's stress as wcll as a lower yaw rate<br />
of lhe car is achievablc.
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comparing the BMw 325i and the BMw 525i on a<br />
wet asphalt track with sinusoidal arrangenrent of bends<br />
show- that the improvemcnt in vehicle stability and the<br />
reduction in stccring effort amount nearly to thc same<br />
value, independently of the highcr adhesion required by<br />
rhe BMW 325i (Fig. l0). Approximarcly 207o reduced<br />
steering cffort and 87o lower yaw ratc wcrc nchieved<br />
rhanks to ASC+T.<br />
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Figure 10. Steering Elfort and Yaw Rate, BMW 325i/525i,<br />
Sinusoidal-Course<br />
Somctirncs pcoplc arguc, thilt the increased stability of<br />
an A, C-cquipped car results froln a rcmrrkably lowcr<br />
nveragc spccd. Fig. II shows a result ohtaincd with thc<br />
BMW 32-5i on a high-spccd handling course. Driving<br />
with ASC indccd rcduces ilverage speed by O5V,-lor<br />
the sake of a 5.3Vo reduccd yaw rilte and a 7.47o<br />
decreased steering effort. This rcsult shows, that the<br />
improvcd vchicle stability inlluenccs vchiclc s;lccd in a<br />
neglectahle way.<br />
I<br />
'oo Steering Effort 1.;ls<br />
o/o Hoduc'tlon by ASC+T<br />
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Flgure 11. High-Speed Handling-Cour$€, Bi/IW 325i<br />
Traction Performance<br />
Section 3: Technical Sessions<br />
By introduction oI a diffcrcntial-brake effect traction<br />
performance improvcs rcnrrrklbly cspecially on split-p<br />
surfaccs. Fig. | 2 shows an exarnplc of trtction inrprovement<br />
on split-p gradicnts ot 12% and l6%. Split-p was<br />
0. l5/0"8, whereby thc low-p wils represented by an<br />
epoxy surface artificirlly watered so that a watcr film ot<br />
constant thickness was qcncrirtcd.<br />
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Figure 12. Tractionon p-Split Gradients, BMW 325i/525i<br />
In case o|tlte l29o grrdicnt the BMW 52-5i was compared<br />
with lnd without ASC+T. Drivcr's bcst ar:hieves<br />
a rlreillr accelcrltion oI I,27 m/sr. whcreby careiul lpplication<br />
of ilccclcrllor pcdal is rcquired. Starting wilh<br />
ASC+T. lhc rrtclrr itccclcr-ation ilmounls to l.-16 rtt/sl.<br />
This improvcmcrtt by 7clo is achievatrle without any<br />
special prccautiort from drivcr's sidc. All these results<br />
were achievcd wilh manurl gcarbox-equippcd cars.<br />
Starting with rr 325i on the split-p 0. l5/0.8 gradient of<br />
l67o without ASC+T wfls not possible. Trying the same<br />
with control system cngaged rcsults in a tncan accclcration<br />
of 0..52 nr/sr. This is a convincing result to which<br />
degree the superiority llso under such cxtrcrllc conditions<br />
is enhanccd by ASC+T.<br />
Simihrly as with ABS llso for ASC+T still somc road<br />
surfaces arc existing, whcrc thc controllcr is askcd too<br />
much. Thcse surl'lccs gcncrllly consist ol' loosc matcritl<br />
likc grlvcl. grit or sundy nurtcrirl. Nornrllly such surfaccs<br />
producc whccl-slip characterislics whcrc t:onlrol<br />
systerns cannol lchicvc optintill utilization of ildhesion.<br />
Wirh rhe IJMW 32-5i as wcll as wirh rhc 52-5i a tcst<br />
wls carricd out on loosc gravel. <strong>The</strong> goal was to accelerarc<br />
thc car fronr O to -500 rn rs fast as possible and to<br />
do sa wilh and wilhoul ASC+T. Fig. l3 shows the<br />
results: driver's hcst in lhis cltsc bcats thc ASCcontroller<br />
by 7% but of course for lhc pricc of incrcrsed<br />
effort for thc clrivcr to kcep the cur in llnc. <strong>The</strong> BMW<br />
525i wilh its higher rcar axle load achieves in this<br />
spcciirl tcrjt a slightly bctter accclcration than thc 325i<br />
(4%).<br />
Cornering<br />
Open-loop and closcd-loop tcstr; on a circle of 66.5 m<br />
radius werc carricd out with a BMW 325i. Thc citr wits<br />
equippcd with ASC+T. whcrcby thc syslcm could be<br />
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switched off. <strong>The</strong> surfacc of the circle consisred of blue<br />
basalt which was permanently watered to reduce its grip.<br />
<strong>The</strong> friction cnefficient was approximatcly 0.3 with some<br />
variations depending on the individual shapc of thc<br />
basalt stones.<br />
<strong>The</strong> car was accelerated on the bluc basalt, until it<br />
reachcd its stationary-limit speed. At a prcdctcrmincd<br />
point of the circle the driver had to apply a stcp input ro<br />
the accelerator. Dcpcnding on the indivirtual test the<br />
driver either had to control the vehicle to keep it in lane<br />
or to fix the steering wheel in fl conslflnl position.<br />
<strong>The</strong> open-loop test provcs, that thc ASC+T-equipped<br />
car holds its coursc without bigger vtriutions in its yaw<br />
rate. <strong>The</strong> car with thc discngrgcd ASC+T shows an<br />
increased yaw rate which ncarly douhlcs within I s<br />
(Fig. la).<br />
Figure 14. Cornering, Open-Loop, BMW 325i<br />
In the closed-loop test with ASC+T the drivcr doesn't<br />
need to correct the steering angle, whcn hc applics a step<br />
input on the accelerator pcdal, bccausc the engine torque<br />
is limited to a non-critical value. In contrast to the<br />
ASC+T not in function the driver starts aftcr 0.5 s<br />
countcrsteering to control the car but again the car cnds<br />
up with a doubled yaw rirtc I s after step input to the<br />
accelerator (Fig. l5).<br />
Results achicvcd with the BMW -52-5i show the same<br />
tendcncy, the ASC+T assists the drivcr vcry strongly<br />
undcr adhesion-critical contlitions driving in bends.<br />
182<br />
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Figure 15. Cornering, Closed-Loop, Step Input to<br />
Accelerator, BMW 325i<br />
Car/Trailer Combination<br />
Vcry often cars are used as tour caravans or boattrailcrs.<br />
Such combinations normally ar.c speed-limited<br />
in most countries becau.se of their morc complicated<br />
road-holding propcrlies. Gcncrally rhe increased rearaxle<br />
load of a cilr towing a trailer does not crcalc traction<br />
problcms, but stability-critical situatiorrs vcry casily<br />
crn be produced by drivcrs nol awltre of the actual adhesion<br />
properlics betwccn tyrc an
etween car and trailer. Within the first 2 seconds,<br />
having slarted turning-off, yaw rate and steering effort<br />
show the same values for the car with and without<br />
ASC+T. After this time the combination starts to<br />
oscillate, because of impaired side stability at the rear<br />
axle of the car without ASC+T. In contrast to this the<br />
carltrailer combination with ASC+T reduces engine<br />
torque during turning off on the changing adhcsion<br />
condition to such an smsunt, that an absolutely uncritical<br />
bchaviour of the combination results.<br />
<strong>The</strong> stability of the combination of a BMW 525i and<br />
a trailer principally shows the same tendency, ASC+T<br />
reduces driver's effort to control the combination and<br />
improves stability.<br />
Avoidance of Accidents by ASC+T<br />
ASC+T can remarkably improve active safety within<br />
the physical limits of tyre/road interaction concerning the<br />
maximum transmittablc longitudinal and latcrirl forces.<br />
Dcpending on their driving experience, thc sflfety margin<br />
of car drivers in different driving situations can differ<br />
significantly. To illustrate this context, Figure l7 was<br />
created. In situations, when no special reactions are<br />
required, average drivers as well as professional drivcrs<br />
control their car within the stable range with sufficient<br />
Safetv reserve.<br />
rffil<br />
lffi;il|<br />
-rfi_il;il<br />
Figure 17. ASC+T, Influence on Dtlvsr's Performance<br />
This situation changes totally, when drivers become<br />
aware of unexpected changes in the normal run of<br />
events. During stability-critical driving manosuvres<br />
experienced drivers in most of the cases will control<br />
thcir car by reducing the safety reserve. <strong>The</strong> average<br />
driver in contrast generally over-rcircts and looscs<br />
control of his car.<br />
Unexpected occurring critical driving situations with<br />
excessive drive-slip are the main field of application<br />
' i<br />
$ectlon 3: Technlcal Sesslons<br />
where ASC+T assists the driver to control his car.<br />
Average drivers will be hindered to inducc instability in<br />
the car, whereas the expcricnced driver automaticillly<br />
will be kept in a more stable range.<br />
ASC+T improves road holding of a car by adhcsionadapted<br />
drive-slip and thus improved driving safety. <strong>The</strong><br />
driver can withstand strbility-critical driving manoeuvres<br />
with reduced physiological stress. Road conditions with<br />
adverse traction potential can be mastered more casily in<br />
superior style. Additionillly drivers can idcntity<br />
adhesion-critical road conditions, the perccption safety<br />
is also improvcd (Fig. l8).<br />
Figure 18. ASC+T, a Contribution to lmprovs Activs<br />
Safety<br />
<strong>The</strong> better knowledge of rond conditions, the physiological<br />
rclief under critical tratfic conditions and the<br />
automatically adapted engine torquc whcn driving on<br />
unexpected changing road condilions hclp lhe driver to<br />
prevent accidents.<br />
<strong>The</strong> accident avoidance potential of ASC+T has not<br />
yet been estahlished cxactly. but can tre cxpcctcd to be<br />
at least as high as with ABS. To promote engineering<br />
work in this field of electronics applicittion is an<br />
important contribution towards iln even safer traffic than<br />
already achieved. <strong>The</strong> introduction of ABS-integrated<br />
drive slip control $ystenrs ASC+T for the BMW 325i and<br />
-525i beside the ASC+T already available for the upper<br />
class modcls of the 7- and 8-series range has to be<br />
treflted as one important stcp towards the penetration of<br />
the wholc modcl range with ASC+T.<br />
References<br />
tll H.J., Krafr, H., Leffler. <strong>The</strong> Integrated Brake and<br />
Stability Control System o[ the New BMW tt-50i,<br />
SAE Paper 900 209.<br />
t21 H. Lcffler, ABS-Integrated Drive Slip Control<br />
Systcms, Evaluation and Performance Comparison<br />
by the Car Manutacturcr, FISITA Paper 905092.<br />
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lSth lnternetlonal Technlcel Conference on Experlmental Safety Vehlcles<br />
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Traction Control Technology for fmproved Driving Safety<br />
Hiroshi Yoshida, Tadao Tanaka,<br />
Keiji Isoda, Koichi Kamiya<br />
Mitsubishi Motors Corporation<br />
Abstract<br />
A traction control system improves vehicle acceleration<br />
and stability; however the traction control system$<br />
alrcady developed have only a slip rcstrictive featurc that<br />
prevcnts wheel spin when a vehiclc starts or accclcrates<br />
on a slippery road surface. This paper prescnts the<br />
advanced traction control system with unique and innovative<br />
technologies, which enables a drivcr to trace<br />
corners safely and smoothly even on a paved road by<br />
prevcnlion of an excessive lateral acceleration. In<br />
addition to vehiclc dynamics, human factors wcrc introduced<br />
to dctcrmine the control algorithm. As a result, thc<br />
system providcd us with an appropriate mental condition<br />
and a further improvement in vehicle mancuverability.<br />
Introduction<br />
Even through the remarkable development of chassis<br />
control technology, driving sirfety should have priority<br />
over any other demand in the recent traffic socicty. From<br />
this standpoint, various types of chassis control $ystem<br />
have been dcveloped to improve vehicle mobility through<br />
the effective utilization of tire forces, which has also<br />
been contributing to the preventive safcty tll t?l.<br />
Namely what these tcchnologies havc been aiming at is<br />
the improvement in thc relationship bctween a vehicle<br />
and a road environment. A traction control system is also<br />
one of those effective methods to improve a vehiclc<br />
maneuverability mainly on a slippery road surface. <strong>The</strong><br />
current traction control systcm recently spreading over<br />
Europe and Japan provides a function that prevents the<br />
driving wheels from developing an excessive slip<br />
through the reduction in traction force (hereinafter called<br />
slip control) [3]. fn this way, the slip control supports<br />
driver's operation, and remarkilble improvements in a<br />
safe driving on a slippery road surface has bcen achieved<br />
without driver's proficient skill.<br />
On thc other hand, evcn on an ordinary road surface<br />
such as an asphalt paved road, a vehicle docs not always<br />
maneuver according to driver's intention under a<br />
marginal turning condition, because tire cornering force<br />
is almost uscd up against an excessive lirtcral acceleration.<br />
In this condition, since the tire slip of driving<br />
wheels is considerably small, it is not significant to<br />
improve a vehiclc controllability by applying the slip<br />
control through the detcction of tire slip. In order to<br />
ensurc a safe driving cven in such a condition, we hitvc<br />
challenged to apply another concept to a traction control<br />
system, which prevents a vehiclc from approaching a<br />
marginal turning condition by regulating traction forcc.<br />
7M<br />
This concept results in the development of an innovative<br />
traction control sy.stem[4]. Thi.s system has ir preventive<br />
safety feature that improves course traceability in a turn<br />
by the automatic regulation of traction force so as not to<br />
generate an cxccssive lateral acceleration (hereinaftcr<br />
called trace control). As a result, thc tracc control<br />
provides a better traceability according to thc driver's<br />
desired courscs in various road surthce conditions. This<br />
also enablcs a vehicle to avoid accidents duc to an<br />
excessiye vchicle speed in a lurn. Namely this system<br />
supports to compensate a drivcr for his operational crrors<br />
for a vehiclc to maneuvcr in a safer condition bcfore it<br />
approaches a marginal turning condition.<br />
Through lhe developmcnl of the control algorithm, it<br />
was found that human factors were tnore importtnl on<br />
such a driver supporting syslctn deeply related to<br />
drivcr's inl'ormation processing, lnd that it is all the<br />
more important to reglrd the relationship bctween r<br />
drivcr and a vehicle as thc closed loop included a road<br />
envircnrncnt as well.<br />
<strong>The</strong> systcm combined thc trace control function with<br />
the slip control function is called TCL. TCL has been<br />
applied to Diamante, Mitsubishi s new car model introduced<br />
into Japanese rnarksl in May of 1990. This paper<br />
mainly dcscribes tho concept and the cffccts of the trace<br />
control concerning active safety that have not been previously<br />
offered by any current traction control system.<br />
Concept of Trace Control<br />
Sleering Charattttristit:s of Fronl Wheel Drive Vehicle in<br />
a Turn<br />
When a vehicle is turning, a lateral acceleration ay can<br />
be formulated by vehicle speed V, stecring wheel angle<br />
EH. etc. as fbllows:<br />
ay = 6H. V2/ {is.L.(l + K.Vz)l<br />
where is = Steering gear rfltio, L = Wheclbilsc, flnd K =<br />
Strrbility factor.<br />
As thc passenger cilr is nonnally designed lo cxhibits<br />
under-steering tcndency (K>O : US characteristics), a<br />
stecring whccl angle incrcitscs according to thc increilse<br />
in vehicle spccd under the conditiorr of the circle lurning<br />
with a fixed radius as shown in Fig. I.<br />
Once a vehicle approaches a mitrginal turning condition,<br />
thc steering wheel has to rapidly incrcascd to trace<br />
a turning circle, which means that thc vchicle hardly<br />
mancuvcrs according Io thc drivcr's intention. Whcn a<br />
vehicle is accclcrated in a marginal condition, that<br />
tendency is slightly strenglhcncd trecause of thc rcduction<br />
in the cornering power of the front tires caused by<br />
a load transfcr flrom the front to thc rear. Furthernrore,<br />
whcn tire slip occurs in such a condition ils snow<br />
covcrcd roads, thc lateral acceleration at a marginal<br />
condition hardly develops in spite of the cxtreme
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E l<br />
g LoU<br />
p<br />
q<br />
Lateral acceleration<br />
'i7'l4 lbrulnal turniE<br />
i/////'j condition<br />
Figure 1. Steering Characteristics of Front Wheel<br />
Vehicle<br />
increase in a steering wheel angle because of the deterioration<br />
of tire s latcral road holding capability. In this<br />
way, since vehiclc controllahility almost deteriorates<br />
near a marginal turning condition, it would bc onc o[ thc<br />
most available approachcs to prcvcnt a vchiclc fronr<br />
approaching a marginal condition for a further sat'ety.<br />
Basic Concept of Trace Control<br />
Rtstriction of Excessive Lateral Aeeeleration.It would<br />
be effective that a vchicle spccd is restricted by the<br />
detection of a marginal condition bclbrc a vchiclc<br />
approaches thrt condition. For examplc, thc autonratic<br />
regulation of traction force according to a dctcctcd<br />
lateral acceleration could prevent a vehiclc from<br />
developing an excessive lateral acceleration, and thirt<br />
would rlciln to prcvcnt a vchicle froln approaching a<br />
marginal turning condition accidentally caused by the<br />
imprudent operation of the accelcrator pedal. Thal rcsults<br />
in giving a driver enough time to control a vehicle safely<br />
and smoothly and thcrcfore could be called a preventive<br />
safety.<br />
Control Reference of Lutral Acceleration Level. ln<br />
order to obtain the appropriate value of a lateral accelcration<br />
for a safe driving, the experiments were carried<br />
out under various driving condilions. Thc concept of<br />
human factors was introduced to set up the rpproprialc<br />
value, that is, the lateral acceleration crilcrion was<br />
derived from the experiments, where a drivcr considcrcd<br />
that he would drive a vchiclc without an excessive<br />
mental tension. (Dcfails conccrning a mental tension are<br />
described below.)<br />
Fig. 2 shows an example of measurcment results<br />
which represents the relationship between a lateral<br />
acceleration and a vehicle specd. It can be seen in the<br />
figurc that the higher is a vehicle speed, the lower is a<br />
lateral accclcration lcvel where a driver negutiates a<br />
corner without an exccssivc mental tension. In urban<br />
areas, a driver seems to have a weak sensation on a<br />
lateral acceleration, which causes a higher allowancc of<br />
a latcral acceleration not to give a driver an cxccssivc<br />
mental tension. It could be why a drivcr receives so<br />
Sectlon 3: Technlcal Sessions<br />
many information to be processed besides a latcrsl<br />
acceleration.<br />
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whtre a cFiver contrcl<br />
o<br />
- " a vehiclg vithout afr<br />
excessive mental trffiion,<br />
Vehicle soeed<br />
Figure 2. Lateral Acceleration Level for Trace Control<br />
Reference<br />
On a winding road. a driver seems to feel a lateral<br />
accclcralion morc .scnsilivcly according lo lhc incrcrrsc in<br />
a vehiclc spccd. Ort it frcc wily, ir drivcr has lhe slrongest<br />
Scnsation on a lateral acceleration. but thc allowance<br />
lcvcl does not seem to vary corresponding to a vchicle<br />
speed. In this way, the referencc level of a latcral<br />
accclcration I'or the trace control was established. whcrc<br />
a driver negotiiltcs a corncr without an excessivc mentitl<br />
tension.<br />
Control Target of Lttngitudinal Acrtlerarfru. From the<br />
viewpoint ol' l driver's operation, the [ollowing typical<br />
pfltlcrns should be considered, where a lateral accclcriltion<br />
exceeds thc rclcrcncc lcvcl as shown in Fig. 3,<br />
where Case A = Increase in steering wheel angle with<br />
vehicle speed constant. and Casc ts = Incrcasc in vehicle<br />
speed with steering whecl angle fixed.<br />
E o<br />
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ol<br />
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Itt<br />
J<br />
Reference longi tudinal<br />
accel erati Dn =oc<br />
Vehicle speed<br />
Figure 3. Typical Pattern$ Which Exceed Reference<br />
Acceleration Level<br />
Whar rhe trace control aims at is to compensate o<br />
driver for fl rcsponss dclay in his operation. So it would<br />
he effective that a vchiclc is dccclerated using cnginc<br />
brrking in case A, and that a longitudinal accelcration is<br />
restrictcd according to the allowrblc longitudinal<br />
acceleration determined bv the estimation of the secure<br />
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lSth lnternetlonal Technlcal Conference on Expertmentat Sefety Vehlcles<br />
time while a driver can afford to control a vehiclc so as<br />
not to exceed the refcrcnce level of a lateral acceleration<br />
in case B.<br />
Thus each refcrencc lateral acceleration level was set<br />
up by cach allowable longitudinal accclcration as the<br />
control map shown in Fig. 4. <strong>The</strong> targct cnginc torque is<br />
finally determined so as to adapt thc rcfcrencc lateral<br />
acceleralion lcvcl to the degree of longitudinal accclcration.<br />
p<br />
rd<br />
L<br />
0<br />
0<br />
U<br />
U<br />
d<br />
d<br />
o<br />
I<br />
Reference lorgifudinal<br />
acceleration =oG<br />
VehiclE EpBBd<br />
Figure 4. Control Map for the Trace Control<br />
Detection of Lateral Attelerailon <strong>The</strong> following<br />
methods have generally been uscd to detect a lnteral<br />
acceleration. Onc is [o usc a latcral acceleration sensor.<br />
and the other is to calculate it from the speed difference<br />
bctween the left and right rotating wheel. Even the<br />
method with a lateral accelerrtion sensor, however, has<br />
a time delay comparcd with the acceleration expected by<br />
a drivcr's steering motion, which could result in the<br />
delay of the control if the methods mentioned above are<br />
applied to the detection of a latcral accclcration as<br />
shown in Fie. 5.<br />
g<br />
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-,* l-ntErnl nri.l.rnti.n dl b. vdiEl! !<br />
.dt!r of flfavlty nnna,rrd hy G s'M<br />
--- - Lit.rit nc.nlnrntrnn r.lldrrntrd<br />
fmm th€ rlfrt and lort rRr<br />
Sssl ScHde<br />
Figure 5. Leterel Acceleration Response for Varioue<br />
Detecting [t/lethods<br />
For this reason, the method was adopted where a<br />
lateral acceleration is obtained from the calculation with<br />
a vehicle specd and a stccring wheel angle in accordance<br />
with Eq. (1). This control with a predictive latcral<br />
acceleration is a feedforward detective one. which would<br />
assure a good control response for the trace control.<br />
Furthermore, this feedforwiud detection mcthod for a<br />
marginal turning condition would bc still available even<br />
on a slippery road surface, such as snow covered road<br />
where an actual lateral acceleration is not well developed<br />
786<br />
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with the increase in stccring wheel angle. That is, a<br />
marginal turning condition is predictivcly detected by a<br />
stecring wheel angle and a vehiclc spccd in any road<br />
condition. Fig. 6 illustrates how thc marginal turning<br />
condition is detected on a slippcry road surface by using<br />
this method.<br />
d<br />
Fd U<br />
il<br />
E g<br />
t-<br />
U<br />
s<br />
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;t'{y'jE wrg," t turnirg condition<br />
Figure 6. Detection of Marginal Turning Condition on<br />
Low u Surface<br />
TCL System Description<br />
Sysfenr ConJigurutittn ttf 'l'CL<br />
<strong>The</strong> schematic diagram of TCL applied to a front<br />
wheel drive vchiclc is shown in Fig. 7. This systcm is<br />
cquippcd wilh various scnsors: lhc rcar wheel speed<br />
sensors for calculating a vehicle speed, the transmission<br />
output shaft speed sensor and the trirnsmission position<br />
signal for a rotating speed of driving wheels, the steering<br />
whccl anglc scnsor for calculltion of a lrteral acceleration,<br />
and the accelerator position sensor for estirnating a<br />
drivcr's accelcrating intcntion. Bascd on those information,<br />
the target engine torque is calculated lry the traction<br />
electronic control unit (ECU), and informed to the<br />
cnginc ECU, which finally controls a cnginc torquc. In<br />
addition the slip ratio of driving whccls is obtained by<br />
compuing a driving wheel speed with a vehicle speed,<br />
which is used as the information of the slip control.<br />
oo<br />
oo<br />
oo<br />
Figure 7. Schematic Diagram of TCL<br />
Control Algorithrn of Trace Control<br />
Fig. 8 shows thc trace control diagrnm based on the<br />
feedforwrrd control of a lateral acceleration described
above. <strong>The</strong> control is performed in accordancc with the<br />
following flow.<br />
. <strong>The</strong> lateral acceleration of a vehicle ay is calculated<br />
with a steering whccl angle 6H and a vchicle speed<br />
V according to Eq. (l).<br />
. <strong>The</strong> reference longitudinal accclcration axr is determined<br />
by V and ay according to the control map as<br />
shown in Fig. 4.<br />
'<strong>The</strong> reference engine torque Tr that realizes axr is<br />
calculated using vehicle mass M,a tire rolling radius<br />
R and a total reduction ratio p, considering various<br />
running resistances, such as a tire rolling resistance<br />
and a corncring drag.<br />
. Thc engine torquc TM that corresponds to the<br />
driver's intention for acceleration is obtaincd by an<br />
accelerator position OA and an engine spccd NE.<br />
. <strong>The</strong> target engine torque TT is finally fixcd by Tr,<br />
TM and corrective factors al and a2, which were<br />
experimcntally dctcrrnined in consideration of a<br />
driver's intention for accclcration. Thc lrflcc control<br />
functions to regulate the engine torquc as far as TM<br />
exceeds Tr.<br />
Figure I. Trace Control Diagram<br />
Superiority of Trace Conlrol to Driver's Operation<br />
It is needless to say that a response delay in a driver's<br />
operation has great influence on a crush avoidance. It is<br />
showed that if a driver's reaction time is shortened by<br />
only half a second, the collision probrbility could be<br />
reduced by a half [5]. So it might be preferable thf,t a<br />
driver gcts rid of a response delay in his operation,<br />
espccially in a trace control marginal turning condition.<br />
<strong>The</strong> trace control compensates a driver for his operational<br />
crror for a vchiclc to mflneuver in r safer condition<br />
bcforc a vehicle approaches a marginal turning<br />
condition.<br />
Fig. 9 shows the breakdown of a necessary time for n<br />
engine torque regulation. As shown in Fig. 9, the<br />
necessary time is reduced considerably by the trace<br />
control with thc fccdforward detection of a lateral<br />
acceleration.<br />
Reliahility of the System<br />
Elcctronic components and sensors of TCL themselves<br />
havc a sufficient rcliability which has already been<br />
developed for the Current chassis control systcms, such<br />
as ABS, 4WD and electronically confiolled suspension.<br />
TCL also has thc following fcaturc to keep a high rcliability<br />
as a total system constitution.<br />
th<br />
trace control<br />
i thout<br />
trace control<br />
sectlon 3: Technlca, sasstons<br />
Cdlculation in ECU<br />
Time(sec)<br />
engine torque control<br />
tion in response time<br />
Required driver's<br />
oFefaf 1 on<br />
Charne in vehicle motion<br />
Figure L Necessary Time for Engine Torque Regulation<br />
. <strong>The</strong> calculation in a engine-ECU and TCL-ECU is<br />
carried out sepffately, which also enables each ECU<br />
to detect some trouble through a rnutual otrservation.<br />
. Troublcs dctection is also madc by various chcck<br />
progrilm through the microcomputer. sensors lnd<br />
actuatorl;,<br />
. Fail-safe is secured to prevent a vehicle behavior<br />
from occurring I suddcrr changc even if the syslcm<br />
fails by somc lrouble.<br />
. When some trouble occurs a driver can easily recognize<br />
the condition with the warning indicator, and a<br />
vehicle is put back to the condition without TCL.<br />
Effect of Trace Control on Vehicle<br />
Maneuverability<br />
Course Trateability under Acteleriltion in a Turn<br />
When a vehicle is accelerated in a circular turn, the<br />
yaw velocity of a vehicle ty increases in proportion to a<br />
vehicle speed V according to the following equation.<br />
V=v/R<br />
where R denotes turning radius.<br />
Hcrc thc coursc trirccability in circular turn would be<br />
evaluatcd by thc dcgrcc of the incrcasc in a yaw vclocity<br />
to a vehicle speed. Fig. l0 slrows thc tcst rcsults thttl thc<br />
vehicle was rapidly accelerated frorn the steady state<br />
circular turn of a 30m rudius with a steering wheel anglc<br />
fixcd. Thc obliquc linc in Fig. l0 indicirtcs thc yaw<br />
velocity when the vchicle lraced the reference circle.<br />
Each pair of plottcrl dala corresponds to the condition at<br />
the start of the acceleration and ilt two seconds after the<br />
start. It says that the smaller the deviation from the<br />
reference oblique line is, the rnore a driver can afford to<br />
conlrol a vehicle. As a result of the tests, thc vehicle<br />
with trrce control had a smlllcr dcviation from thc<br />
referencc line, which mcflns a hcttcr coursc traceability<br />
than that of the vchiclc without thc tracc control.<br />
Operation of Steering Wheel and Atceleralor Pcdal<br />
Effett on a Operation Manner. Fig. I I and Fig. l2<br />
present the cffcct of thc trace control on thc manncr of<br />
operating r stecring whcel rnd ln accelcralor pcdlll in<br />
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13th lnternetlonel Technlcal Conference on Experlmentel Safety vehlcles<br />
0<br />
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r with traca Eontrol<br />
o wrthout trace control<br />
-..r#j)-<br />
/ Start of \ / 2 seconds \<br />
\acceleration/ \ after start /<br />
-"\B<br />
Figure 10. Course Traceability During Acceleration in a<br />
Turn<br />
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P E<br />
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0<br />
5<br />
P Io0<br />
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0 b<br />
a human being receives an emotional stimulus, he reacts<br />
physiologically such as heart rflte, r galvanic skin<br />
rosponse and a brain wave. Fronr the vicwpoint of<br />
quantitative and continuous measurcmcnt, a galvanic skin<br />
response was applicd, which is utilized the physiological<br />
phenomenon that a cell depolarizltion by receiving an<br />
emotional stimulus causes the viuiation ol'a skin clectric<br />
resistance, so-callcd a skin impedancc level. Fig. l5<br />
shows a measurenrent example o[ skin impcdancc lcvcl<br />
on the winding road driving shown in Fig. 14. In Fig. 15,<br />
thc vertical axis represents the degree of mental tension<br />
in a dimensionless form, and the higher a vertical level,<br />
the lower a skin impedance level and the higher a<br />
drivcr's mental tcnsion. <strong>The</strong> experiment were carried out<br />
under thrcc control references. that is A . B . C as shown<br />
in Fig. 15. It is tound that a driver's mental tension is<br />
greatly affected by thosc control references, and ir is<br />
considerably decrease so long as suitable control<br />
condition would be applicd. As shown in Fig. 15, "8"<br />
would give a driver an appropriatc mentrl tension. It<br />
would bc why a driver has no need to process the<br />
information for road holding condition. Namely a drivcr<br />
can afford to pay more attention to a coursc tracing and<br />
a crash avoidance.<br />
o<br />
F-H:<br />
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frE= ft<br />
I<br />
n c<br />
o -F<br />
€&<br />
ETE<br />
g#5<br />
with trac8 control<br />
withilt trlEE mntrcl<br />
Figure 14. Driving on Winding Road<br />
tr<br />
cl<br />
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E<br />
L<br />
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'tt 9l<br />
.EH<br />
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J<br />
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measurement resul ts<br />
Vehicle speed<br />
,E-<br />
{CflE}<br />
c<br />
{} Reti=xation<br />
trace control<br />
Figure 15. Efloct of Trace Control on Mental Ten$ion<br />
Sectlon 3: Technical Sessions<br />
In addition anothcr r*oru.*rnrnt regarding a driver's<br />
physiological responsc was tricd, that is, an eleclrocncephalogram<br />
(EEG): brain wave. Fig. l6 shows the<br />
analyzed results of EEG rncrsured on thc winding road<br />
shown in Fig. 14. As shown in Fig. 16, the tracc conlrol<br />
workcd to rcducc lhc 1rclwcr ol EEG in thc rangc ol p<br />
wavc (14*50H2.), which nrclns thflt lhc irctivc lcvcl o[<br />
the brain was approximatcly kcpt in lhc slrne condition<br />
as thc driving on il $traight road, or not cxccssivcly.<br />
Freqnrny(Hz)<br />
Frequency (Hr)<br />
FrequEncy( Hr )<br />
(a)l'/ith trace control<br />
(b)Without trace control<br />
(c)Drivirg<br />
//<br />
- E{t.o<br />
dBV<br />
-5dn<br />
dBv<br />
Figure 16. Eflect of Trace Control on Mental Tension<br />
(Brain Wave)<br />
Conclusions<br />
Allhouglr a trigh pcrformance vehicle shows an excel-<br />
Ient mobility, it rlso has a high possibility to lpprolch<br />
a marginal driving condition. cspcciirlly in a lurn. Once<br />
a vehicle enlcrs a margintl condition, ir driver has hardly<br />
enough timc lo control a vchiclc. From this standpoint it<br />
is thc mosl effectivc that a vchicle never lpproachcs a<br />
marginitl condition and a driver ncvcr has an cxcessive<br />
mental tcnsion. This conccpl hts bcen lpplied to rhc<br />
traction control tcchnology undcr the name of trace<br />
control. Narnely in thc construclion of thc trilclion<br />
conllol algorithrn, hurnln l'lctors such ls a drivcr's<br />
mental strcss wcrc tlso irrtroduccd in addilion to the<br />
improvenrcnt of vchiclc dyrrantics. Tlrlrt itlso rnoans lhitl<br />
lhe syslcm hus bccn built up lly rcgrrding lhc rclltionstrip<br />
bclwccn a drivcr and a vchiclc a.s lhc closcd loop<br />
includcd a road cnvironrttcrtl irs wcll.<br />
Thc lcst rcsull provctl thitl thc lritcc conlrol contributcs<br />
to lhc rcduclion not only in u drivcr's physical load hut<br />
also in a mentill lcnsion with good traccability kcpt.<br />
Furthermore. those cl'l'ccts would mcan thrt thc trlcc<br />
control secures the enough tirne l'or a drivcr to rccover<br />
a vehicle rllaneuvcr evcn il'any crrors arc nradc in a<br />
sleering and un ucccleraling opcration. It would bc lust<br />
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lSth lnternatlonal Technlcal Conference on Experimental Satety Vehlcles<br />
a preventivc safety or an active safety. In that sense the<br />
trace control could bc one of the most innovativc<br />
systems for further improvcmcnt in driving safcty.<br />
Lastly, wc authors arc sure that the rellization of this<br />
prcvcntive or activc safety concept indicates thc stitrting<br />
point of a new gcncration: Human-oriented vehicle.<br />
References<br />
l. R. Mitamura, M. Tani, T. Tanala, & H. Yuasa:<br />
Syslcm intcgration for New Mobility, SAE Paper<br />
8E1773 (1988).<br />
s7.o.04<br />
Controlled Suspension for Better Safety<br />
Jean-Pascal Reille, Charles Blanot<br />
Renault Direction des Etudes<br />
Abstract<br />
<strong>The</strong> field ofcontrollcd suspension is dcvcloping rapidly.<br />
By improving the trade off between ride comfort and<br />
handling, such systems have bettered the global car<br />
performance. Up until now, controllcd suspcnsion made<br />
it possible to ilnprove colnfort and perforrnance in most<br />
cases, with thc result being at least equal to thflt of the<br />
rcfcrcncc passive suspension vchicle. <strong>The</strong> new system<br />
described here affords superior passenger cornfort and<br />
safety irrespective of the road protile and driving<br />
situation. <strong>The</strong> experimental vehicle huilt by Renault,<br />
which was developed in conjunction with Lipmesa associated<br />
with Sagem, is equipped with four quick-acting<br />
variable-darnping shock ahsorbers. <strong>The</strong> darnping force is<br />
controlled in real timc on thc bflsis of informrtion<br />
qualifying the pilot's driving, e.g. steering-wheel<br />
information, and information ohtained from the road<br />
protile, such as the absolule crr-body and whccl vclocity.<br />
<strong>The</strong> set value of force is calculated tilking into<br />
account the velocity of shock absorber displacement and<br />
the map of its frlrce-velocity pattern. <strong>The</strong> results of the<br />
simulation calculations and the dynamic tests performed<br />
on the vehicle show the effectivcness of this ncw concepl,<br />
which providcs a subslantirl improvcmcnl in sflfcty<br />
combined with increased comtbrt.<br />
Introduction<br />
<strong>The</strong> numbcr of controllcd suspcnsion systems on olfcr<br />
is incrcasing. Such systcms givc an improvcnrcnl in<br />
ovcrall vchiclc pcrformancc, cspccially for slrongly<br />
characterized road or driver stresses.<br />
Very often, however, when the shock abstlrber allows<br />
only discrctc scttings, thc systcm l-ixcs a rncan calibration<br />
position which thcn givcs a rcsult similar to that<br />
obtaincd with a standard vehicle.<br />
To allow simultaneous improvement of cornfort and<br />
road holding, a system must be dcveloped lo allow rell-<br />
790<br />
7 H. Yoshida and M. Tani: Futurc Trcnds of Vehicle<br />
Control Technology, Journal ol'JSAE, Vol. 43, No.<br />
I, 1989 (in Japanese).<br />
3. H. Demel and H. Hemming: ABS and ASR for<br />
pa$senger cars-goals and linrits, SAE 890834, 1989.<br />
4. K. Isoda, M. Osaki, M. Hitshiguchi, & K. Otake:<br />
Mitsubishi Traction Conlrol Systcm (TCL) and<br />
Chrssis Integrated fklntrol Technology, Mitsubishi<br />
Motors Tcchnical Rcvicw. No.3. 1991.<br />
5. Hans-Georg Metzler: Computer Vision Applied to<br />
Vehicle Opcration, SAE 881167, 1988.<br />
time control of damping forces. We therefore selected<br />
quick-lcting variable-damping shock absorbcrs which, in<br />
associlrtion with an original control stratcgy, are<br />
undoubtcdly the ne plus ultra in controlled damping<br />
suspcnsion systcms.<br />
Thc vchiclc uscd for the study is a Renault 19, and an<br />
application ol this concept is inrlllcncntcd on the<br />
Renlult Cover safety vehicle. This application is implcmented<br />
taking into uccounl the industrial constraints for<br />
a vehicle of the Rcntult ranse.<br />
System Architecture<br />
<strong>The</strong> systern installcd on thc vchicle is shown in Figure<br />
t.<br />
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Figure 1. System Architecture<br />
Sensors<br />
<strong>The</strong> following information is used in lhe $trategy;<br />
. 4 whccl/body displaccmcnts<br />
.4 body vcrlicrl accclerrtions ,<br />
. Stccring-whccl posilion<br />
. Throttle-valve position<br />
. Longitudirral lccelerorneler<br />
. Vehiclc spccd.<br />
Shock Ahsorhers<br />
For optimum performance the shock absorber must<br />
havc the largest possihle sening dynamics and the
shortest possible response time. <strong>The</strong> damping force must<br />
be as close as possible to the calculated force, and it is<br />
advisable to have numerous possible shock absorber<br />
settings. A continuous variablc-damping shock absorber<br />
was therefore selccted.<br />
An oil flow between the rebound chambcr and the<br />
shock absorber reserve chamber is controlled by solenoid<br />
valve. This allows damping forces to be varied both in<br />
expansion and compression. To avoid changing the existing<br />
shock absorber structure, oil passes through a<br />
counter-rod. <strong>The</strong> control valve is incorporated at the top<br />
the rod. A cross section vicw of the shock absorber is<br />
shown in Figure 2.<br />
mntrol valw<br />
7684ru8 dEmbr<br />
rabound chamber<br />
d8bn rod<br />
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Flgure 2. Damper Crose Section<br />
<strong>The</strong> shock absorber's response time is l0 ms. It is<br />
important to obtain a minimal phase shift between the<br />
damping forcc required and the force obtained.<br />
Control Strategy<br />
Vertical Striltegy<br />
<strong>The</strong> control strategy ensures independent, real-time<br />
control of the damping force on each wheel. <strong>The</strong> optimum<br />
damping forcc one wishes to obtirin at each<br />
moment depends on the absolute wheel vclocity, V*,*.,<br />
and body velocity V*0, of the vehiclc quarter in<br />
question.<br />
F=Cr*V**.,-Cr*V*0,<br />
<strong>The</strong> difference of this strategy by comparison with the<br />
usual<br />
"skyhook"<br />
type patterns is the addition of the tcrm<br />
Cr * V*b"o' which allows a compromise to be reached<br />
between wheel grip (safety/performance) and body<br />
moyements (the comfort achieved being weighted by the<br />
term C, * V*or). This compromise can be shiftccl from<br />
one pole to another by adjusting the coefficients C, and<br />
: Sectlon 3: Technlcal Sessfons<br />
C, an increase in cocfficient C, displaccs this compromise<br />
towards the "safely" polc, while an increase in<br />
C, displaces it towards the "comfort" pole.<br />
Safety Slrategy<br />
Driving situations are detected by the foltowing<br />
paramcters;<br />
. Steering,-wheel position, Can detect that the vehicle<br />
is in a cornering situation. In this case, it must be<br />
possible to increase the transverse capability for<br />
trflnsmitting tyre force.<br />
, Steering-wheel slteed. Can dctect emergcncy collision<br />
avoidance manoeuvres when it is necessirry both<br />
to increase tyre capacities and limit the vehicle's roll<br />
velocity.<br />
. Throltle posilion. This variablc makes it possible to<br />
know the engine torquc demanded by the drivcr and<br />
to increase the tyrc's longitudinal capability.<br />
. Throttle speed. Allows detection of engine torque<br />
variations which could generalc a vehiclc pitch<br />
_ motion.<br />
, Longitudinal acceleration. Allows detection of braking<br />
situations where it is necessary lo increase lhe<br />
vchicle's longitudirral capability. This scnsor could<br />
bc replaced by a braking pressure rncasurement.<br />
<strong>The</strong> choice of thc pair of coefficients (C,, Cr) is<br />
determincd from thc preceding parameters and the<br />
vehiclc speed. For strlight-linc driving, thc compronrise<br />
centres on the comfort coel'ficicnt, and C, is therefore<br />
very snrall. When onc of the parlmeters excccds a predefined<br />
threshold, the pair (C,, Cr) is altercd in order to<br />
improve vehicle safety. For multiple stresses, the pair of<br />
coefficients offering the greatest safcty is adopted. <strong>The</strong><br />
coefficient pair (C,, C2) is spccific to each suspension<br />
train.<br />
Wc can take as nn example the operation of the<br />
system on cornering, where driving silfety is to be<br />
increascd. In the [steering-wheel angle, vchicle speed]<br />
plane, four threshold levels are defined, thus defining<br />
fivc coefficicnt pairs (see Figure 3). When the Isreeringwheel<br />
angle, vchicle speedl operating point enters a<br />
region, the coefficicnt pair for the region in question is<br />
applied to the force calculation. This allows a gradual<br />
change of thc comfort/perfornrance compromise. Whcn<br />
dsgra<br />
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the thresholds are crosscd downwards, a time lag is<br />
applied.<br />
Shock Ahsorber Control<br />
Once the damping force has been calculated, the<br />
actuator control current is determined. A shock absorber<br />
control map, determined by machine tests, is stored in<br />
memory. With this map, knowing thc shock absorber's<br />
displacemcnt speed and thc force rcquired, it is possible<br />
to calculatc the control current. Spccific maps exist for<br />
the front and rear susPensions.<br />
It may be that thc calculated forcc is not attainable:<br />
. either because it docs not come within the shock<br />
absorber's setting ranBe;<br />
. or because it is in the "activo" part of the forcevelocity<br />
plane (this is the region in which cnergy<br />
woukl have to be applied to achieve the required<br />
force).<br />
Figure 4 illustrates this phenomenon' In the force/<br />
velocity plane are shown thc operating points requircd by<br />
the calculation, for a "bad road" type of cxcitatiort' This<br />
is an eloquent dcmonstration of the diffcrence bctween<br />
an activc suspension and a semi'active suspension'<br />
LilVbAI'FIIIB<br />
HIGH DAMPING<br />
Figure 4. Damping Forcs Hsstriction<br />
In both these cases, the strategy selects the control<br />
current so as to minimizc the diffcrence between the<br />
force exerted and the desircd optimum force'<br />
192<br />
<strong>The</strong> entire loop, from the choice of coefficients<br />
through to suspension cotrtrol, is implemented in less<br />
than l0 ms. <strong>The</strong> flow chart of the control strategy lor a<br />
vehicle quarter is shown in Figurc 5'<br />
Figure 5. Gontrol Algorithm<br />
Simulation<br />
In the initial phase, the calculation made it possiblc to<br />
validatc the control striltcgy defined above. Subsequently,<br />
the calculation was u$ed to define the sy$tem profile:<br />
response timc, sensor precision, and numcrical calculus<br />
mcthods. Ultimately, calculation is a tool allowing predefinition<br />
of the strategy cocfficicnts so its to reduce the<br />
timc rcquircd for development tests.<br />
Figure 6 shows an example in which the obstaclc<br />
adopted is a road ltuntp ol' wavclength 40 m. Onc<br />
observes that thc constant increasc in cocfficicnt C2, Cr<br />
6.00<br />
F=C1*Vwheel-C2*Vbody<br />
icontrol current<br />
dePendant on<br />
F and wheel/body VelocitY<br />
mDY AccELERAmN (m/r4<br />
Figure 6. Road BumP ResPonse
constant, produces a major reduction in vertical acccleration<br />
of the vehicle when passing over the obstacle.<br />
Test Results<br />
All the tests performcd showed the tdvantages of this<br />
typc of suspension system, from both the safety and<br />
comfort vicwpoints.<br />
<strong>The</strong> gains achicvcd include the following:<br />
. straiEht-line uavel: reduction in low-frequency body<br />
movements, and reduction in car vibration levels:<br />
. braking: reduction in dive effect, irnproved road grip<br />
by thc wheel, especially on poor roads;<br />
. acceleration: reduced nose-up, improved traction;<br />
, rornering: rcduction in spurious body movements,<br />
improved control of wheel grip especially on bad<br />
roads. Improved body behaviour when negotiating a<br />
corner.<br />
It can therefore be seen thflt major gains are achieved<br />
in all customary drivilrg conditions.<br />
Comfort Tests<br />
Gains in comfort are illustrated particularly well by<br />
Figure 7. This tcst was performed on a four-cylindcr<br />
hydropulse bcnch. <strong>The</strong> figure shows a comparison<br />
bctwcen the vertical acceleration spcctra at the body<br />
levcl for a "rolrd" type signal on a car body equipped<br />
with a standard passive suspension systern or the cartographic<br />
suspension systcm.<br />
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Figure 7. Comfod Bench Test<br />
Cartographic suspension gives a lower accelerometric<br />
level at mcdium and high frequencies than thc smndard<br />
suspension system, without detracting from lowfrequency<br />
movements. This results in bcttcr ovcrall<br />
comfort and hence lcss driver fatigue.<br />
Performance I'ests<br />
An example of a gain in vehicle pcrformancc is shown<br />
in Figurc 8. <strong>The</strong> test involves a lanc change at 80 km/h.<br />
Thc rcsultant roll velocitics for a standard suspension<br />
and the cartographic suspcnsion are compared (these roll<br />
3: Technlcal Sesslons<br />
velocities were measured by an incrlial unit). A major<br />
reduction in roll velocity is obscrvcd with thc cartographic<br />
suspension system. This will lnean a far bctter<br />
subjcctivc impression frlr the driver and, once again,<br />
improvcd driving comfort.<br />
Figure B. Lane Change Test<br />
Real-tinre control of lhc vcrtical force applied to the<br />
tyre allows the stopping distance on a poor rold to be<br />
reduced by comparison with a standard vchiclc. This<br />
means a 20Vo rcduclion in deterioration of stopping<br />
distancc duc to a degraded road surl'acc. Of course, this<br />
result dcpcnds on lhc severity of the road profilc.<br />
Conclusion<br />
ffiffi<br />
FO|.l VELOCTTY<br />
This cartograph ic suspension system is thc most<br />
sophisticatcd industrial controlled damping system availablc<br />
trtday. <strong>The</strong> strategy dcscribcd hcrc could be still<br />
furthcr inrproved, while retaining thc stmc number of<br />
sensors, to allow fincr nrolritoling of roll and pitch<br />
modes.<br />
Thc quick-acting cflrtogrilphic suspcnsion system, with<br />
extensive setting dynrrnics, providcs the optirnunt rnatch<br />
belween the danrping l'orce cxerted anrJ thc darrrping<br />
force required. This l'cirturc makes it possible to obtain<br />
exceptional pcrlormance in terms of safety, on thc onc<br />
hand hy improvcd vehicle control and on thc othcr hund<br />
by reducing the vibrttion lcvel, which is a sourcc of<br />
fatigue.<br />
<strong>The</strong> system in its prcscnt configuration is homogeneous,<br />
since there is a ntiltch bctwccn thc number and<br />
qurlity of sensors, and the octuttor pcrformance. This<br />
solution can hc rcgardcd as an envelope solution which<br />
will have to be brokcn down into various systems,<br />
adapted to each vehiclc rflnge, according to a compromisc<br />
ccntcring around three main criteria: complcxity,<br />
cost and pcrformtnce.<br />
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1lth lntemetlonat Technlcal Conference on Experlmental Sefety Vehlcles<br />
s7.o.05<br />
Improvement in High-Speed Safety Through Active Suspension Control<br />
Naoto Fukushima, Namio Irie<br />
Nissan Motor Co.. Ltd.<br />
Abstract<br />
This paper dcscribes the hydraulic active suspcnsion<br />
which is mountcd in the Nissan Infiniti Q45 and is<br />
effcctive in improving high-specd safety' This active<br />
suspension has been dcsigned specifically to provide<br />
improved vehicle stability al high speed through the use<br />
of skyhook damper control, a frequcncy-dependent<br />
damping mechanism and active roll and pitch control'<br />
<strong>The</strong> system design concept is prcscnted along with an<br />
analytical explanation of the three major functional<br />
featurcs. <strong>The</strong> results of theoretical and expcrimental<br />
analyses are prescnted which clarify quantitatively the<br />
effects of the control procedures and parameters on thc<br />
vcrtical vibration charactcristics of thc vchicle body<br />
during high-speed driving, as wcll as on the road contact<br />
of the tircs when traveling on an undulating road, crosswind<br />
stilbility and stecring responsc characteristics'<br />
<strong>The</strong>se results confirm that this active suspension<br />
provides outstirnding performance unobtainallle with<br />
conventional suspensions, espccially undcr high-specd<br />
driving conditions.<br />
Introduction<br />
Activc suspensions have become a central focus of<br />
passenger car chassis dcvelopment today becausc they<br />
hold out the potential for achieving dramatic improvements<br />
in performance oYer conventional passive control<br />
systems. <strong>The</strong> lattcr have mainly controllcd vehicle<br />
motions by switching the spring and damper rates<br />
according to the condition ot the vehicle.<br />
Research on active suspcnsions dates back approximately<br />
twcnty years and was originally aimed at application<br />
to railway vehicles Il]. <strong>The</strong> first serious attempt to<br />
apply an active suspcnsion to the automobilc was a<br />
mechanical system dcveloped by Automotive Products<br />
Co. which was based on a hydropneumalic suspension<br />
[2]. Subsequently, Lotus developcd an activc suspension<br />
incorporating an electro-hydraulic servo systetn. <strong>The</strong><br />
Lotus suspcnsion has bccn tested in sports cars and also<br />
installed in racing cars [3].<br />
More recently, Nissan and Toyota successively<br />
announced hydraulic active suspensions for certain<br />
passcnger car modcls t4l t51 and thus ushercd in an erit<br />
of active suspension use in production vehicles-<br />
This paper first discusses thc types and features of<br />
typical active suspensions developed to date and then<br />
describes the Nissan hydraulic active suspension<br />
installed in the Infiniti Q45 sedan. <strong>The</strong> construction of<br />
the system is presented along with an analysis of its<br />
performance charactcristics, the design method used, and<br />
794<br />
the system's contribution to improvements in vehicle<br />
dynamics.<br />
Types and Features of Hydraulic Active<br />
Suspensions<br />
Three typical types of hydraulic active suspensions<br />
that have been devcloped to date arc classified in Figure<br />
1.<br />
TYPe Configrrtion F6aturos<br />
A<br />
(Lotus)<br />
B<br />
NIssan<br />
G<br />
(A.P, )<br />
VaIv6<br />
controllor<br />
Dj-r6cty Linkefl<br />
Cllirder anal YalYo<br />
High Rosponsc<br />
Servo Valve<br />
'Foedback $De<br />
Press\r.re CcntJoI<br />
Valve<br />
'oonpact AccuEulrtoJ<br />
{br Reflucing<br />
Pr6ssure<br />
Fluctuations<br />
Figure 1. Configuration of Typical System<br />
IuproY€d<br />
Hydro PneuEatic<br />
Susponsion<br />
Type A, a system under developmcnt at Lotus' is<br />
charactcrized by its direct linkage of a double-acting<br />
cylinrler and a high'response control valve- While the<br />
control capability of thc system is quitc high' the control<br />
valve must provide fimt respotlsc in order to absorb<br />
vihrational inputs fronr the road surface- As a rcsult' the<br />
system neccssarily consumes a large alnount o[ energy<br />
espccially on rough road surfaces where unsprung<br />
rcsonance is conspicuous.<br />
Type C was a hydropneumatic suspension developcd<br />
hy Automotive Products and was constructed as a hydropneumatic<br />
suspension. It employed a flow control valve<br />
to itccomplish active control by filling the accumulator<br />
and sending the hydraulic fluid to the cylinder' Bccause
of this method of operation, it consumed a great deal of<br />
energy in controlling bounce, roll and other sprung<br />
motions that occur during travel on an undulating road<br />
surface or in slalom-like driving.<br />
Type B has been developed by Nissan with the specific<br />
aim of suppressing the increase in energy consumption<br />
seen with the other two types. One of its major<br />
features is the combination of a pressure control valve<br />
with a small accumulator and a hydraulic cylinder.<br />
Vibrational inputs from a rough road surface are absorbed<br />
by the accumulator, which reduces thc flow ratc<br />
rcquired of the system as a whole. Control of sprung<br />
vibrations is accomplished by active damping control and<br />
thc passive damping action of the hydraulic system to<br />
reducc the required hydraulic fluid flow rare when<br />
travcling on undulating road surfaces. Thus, the large<br />
energy consumption that becomes a problem in the type<br />
A and C systems under certain driving conditions is<br />
avoided. In terms of ovcrall cnergy consumption, type B<br />
can be characterized as an energy-saving active suspension<br />
system.<br />
<strong>The</strong> following discussion will describe the type B<br />
system featured in the Infiniti Q4-5 as a rcpresentttive<br />
example of active suspension systems.<br />
Construction of Hydraulic Control System<br />
Required Control Systenr FuncIion<br />
One major feature of active suspension control is that<br />
the active elemcnt added to the system necessarily becomes<br />
an element that transmits road surface inputs. as<br />
seen in Figure 2. Consequcntly, the actuator used in tn<br />
active suspension must be capable of both gcncrating the<br />
necessary force to control sprung motions and counterbalancing<br />
vibrational inputs from the road surface. In<br />
developing the control system for the flctive suspension,<br />
this was both the mo.st critical and the most difficult<br />
issuc that had to be addressed.<br />
lxz<br />
Control Sfglf,l<br />
Id€aI Acturtor<br />
l*,<br />
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(a) Paesive Suepenaion (u) Active Suspension<br />
Figure 2. $uspension Modol<br />
A great deal of theoretical research has been conducted<br />
on active suspensions and there are many reports<br />
in the literature of analyses involving the use of an ideal<br />
acluator t61 t71.What is meant by an ideal actuator is<br />
one that generates force according to contfirl inputs but<br />
Sectlon 3: Technlca, Sessrons<br />
does not produce any relctive force against vibrational<br />
inputs from the road surtace. <strong>The</strong> function requircd of<br />
the control systcm of irn uctive suspension therelbre<br />
differs from that required of an ordinary servo system.<br />
H ydrauli c C o nt ro I Sy st em C onfi gur ation<br />
In actuality, the hydraulic control system is conl-igurcd<br />
such that it includes dampers, in addition to an ideal<br />
actuator. A detailcd system configuration is shown in<br />
Figure 3.<br />
-Pilot Valvo<br />
soranoial I lhin Yalvo<br />
spnrlt; rr5lt<br />
Aoclmhtor<br />
DrDpirl8 valva<br />
Pressure Control System<br />
As indicated in thc figurc, high-pressurc hydraulic<br />
fluid is sent frorn the purnp and introducccl through the<br />
main valvc. fronr whcre it is sent to the wheel actuator.<br />
Whcn thc spool is in a neutral position, the valve is<br />
completely closed. Movcment of the spool to the right<br />
opens the port on high-pressure side. Conversely, when<br />
the spool lltoves to thc lcl't, thc rcturn-sidc port is<br />
opencd.<br />
<strong>The</strong> cylinder pressure is fed back and applicd to the<br />
right cnd of the spool, while control pressure produced<br />
by the solenoid and pilot valvcs is applied to the lcft<br />
end. When the two pressure levcls arc unbalanccd, the<br />
spool moves accorclingly, changing thc cylindcr prcssurc.<br />
As a rcsult, the spoc'l roturns to its neutral position and<br />
the cylinder pressure is thus regulated so that it is equal<br />
to thc control prcssurc.<br />
<strong>The</strong> accumulator and hydraulic cylinder are connected<br />
by means ol' a darnping valvc. As will bc explained in<br />
detail in thc l'ollowing scclion, the plrssive damping<br />
action of lhe hydraulic aclivc suspcnsion is produccd hy<br />
a system which conrbines this darnping valve wirh rhe<br />
accumulator tnd the pressure conlrol valve. This results<br />
in an idcal frcqucncy-dcpcndcnt damping characteristic.<br />
Basic Chararrlrri.sricJ oJ' Hytlraulic Control System<br />
This section explains two typical characteristics of the<br />
active suspcnsion control systcrn. Onc is thc rcsponse<br />
characteristic of the force F2 generated try the cylincler<br />
in relation to the control currcnt, i. Thc othcr is the<br />
charactcristic of thc l-orcc F2 gcncrfltcd by thc cylindcr<br />
in relation to the vclociry, xl - x2, which concsponds ro<br />
road surface inputs. Experimenttl data on these two<br />
characteristics rrc shown in Figure 4. <strong>The</strong> pirflmeter<br />
denoted as Po in the figure indicares the biased hydraulic<br />
pressure.<br />
<strong>The</strong> i-F2 characteristic shows sufficient responsiveness<br />
to control the pitch, roll and bounce motions of the<br />
795<br />
:A<br />
:.td
lflth lntematlonal Technlcal Conference on Experlmentel Safety Vehicles<br />
tr<br />
G<br />
b l|)_<br />
tt<br />
fr-r<br />
d<br />
fi-r<br />
0<br />
-20<br />
-40<br />
0.1<br />
0T<br />
50f<br />
oof<br />
F 2.5<br />
h<br />
f; 20<br />
.x r_ 1.5<br />
.11<br />
\ B; 1,0<br />
Po:6. 2 MPa<br />
Po -'4 7 MPa<br />
Po :4.0 MPa<br />
t0<br />
50F T<br />
0.1<br />
I l0 IIE<br />
6J 4\<br />
0<br />
' o<br />
h0<br />
,g -10<br />
s -20<br />
$ -30<br />
(a) Force<br />
Fz/Control Signal i<br />
r+ 4<br />
t0<br />
llr,<br />
2 1 0 H 2<br />
(u) r'oree Felverocitv(ir-r?e )<br />
Figure 4. Frequency Response of Electrohydraulic<br />
System<br />
vehiclc body. <strong>The</strong> charactcristic of F2 in rclation to<br />
xl - x2 shows a damping tcndency, the value of which<br />
becomes smallcr at higher frcqucncies. This result indi'<br />
cates that the transmission of road surface inputs to the<br />
body is reduccd in the high frequcncy region.<br />
I n-V e hic le C o nfi guration<br />
<strong>The</strong> layout of the system when installed in a vehicle<br />
is shown in Figure 5. All of the major componcnts wcre<br />
newly developed tor thc hydraulic activc suspension.<br />
Analysis and Design of Hydraulic Active<br />
Suspension<br />
This section explains the procedure followed in<br />
designing the hydraulic active suspension. First, an<br />
analytical explanation is given of the thrcc major<br />
functional features of the systcm-skyhook dampcr<br />
control, frequency-depcndent damping mechanisnt and<br />
roll/pitch control. <strong>The</strong> concept applied in delcrntining<br />
their control con$tants is also explaincd. After that. an<br />
explanation is given of thc pcrlormance charactcristics of<br />
the mechanical suspension used in conjunction with the<br />
?96<br />
O reedback I:rpe F€ssure Control Valve<br />
€) Fadill Plunger Puup I 7 cylirders' l0Mh<br />
(D Accunrrlator i f'ree Piston ffPe<br />
(D Controller : Built in lfigl Speetl 16 bit CPU<br />
CS Acceleronctor ! Ball Detection $rye<br />
Figure 5. Schematic Diagram ol Active Suspension<br />
System<br />
hydraulic active suspcrtsion and of thc sharing of the<br />
perfurmancc load betwecn thc two systems.<br />
Skyhook [)amprr Control and Freqwnr:y-Dependenl<br />
D antp i n.q, M t t: hu tti snt<br />
Thc comhination of skytrook dampel control and thc<br />
frequcncy-dependent damping tnechanism is notably<br />
effective in darnping both thc sprung and unsprung<br />
resonances of thc vchicle and in rcdrrcing thc transmission<br />
of roatl surlace inputs to tho body. <strong>The</strong> tollowing<br />
cxplanation inilicates how this is accornplished.<br />
Skyhook tluntper ronlrttl. It hns been noted thilt a<br />
skyhook darnper, which produces damping forcc in proportion<br />
to the absolulc vcrtical velocity of thc vclriclc<br />
body, is a ration:ll approach to rcducing body vibration<br />
[6]. This concept has bccn incorporated in the hydritulic<br />
control systcm ol' the Nissan activc suspension. <strong>The</strong><br />
equivalent urodcls shown in Figuro 6-(c) and (d) were<br />
uscd in analyzing the chrrrclcristics of a passive dlmper<br />
and the skyhook dantper. When it pirssivc damltcr is<br />
employed, thc vcrtical vibrittion chnractcristic of the<br />
hody in rclfltion to road surface inputs is given by<br />
*r=. zjor("or*c,rl<br />
'.' Effi<br />
<strong>The</strong> vibrnlion lrnnstrtission rillio ltl thc rcsonnni point is<br />
(l)
t<br />
I<br />
t<br />
I<br />
kql'rlad ldrl<br />
r'l ---r--I<br />
r,t Flc,<br />
o r -rrri,ili<br />
6-c/{hffi}<br />
I<br />
T ,<br />
-a<br />
Figure 6. Conliguration and Characteristics of Skyhook<br />
Damper<br />
, lT<br />
,T'-* =Jt.ft<br />
and it always has a value greater than l.<br />
With the skyhook damper, on the other hand, the<br />
vibration characteristic is givcn by<br />
*,<br />
=<br />
27ror(rro +of<br />
.xr +rt * Z.lroz 1(, +(") (3)<br />
o +col<br />
<strong>The</strong> vibration lransmission ratio al the resonrnt point is<br />
<strong>The</strong>refore.<br />
,xa,<br />
lTl**,<br />
*l<br />
(,><br />
(2)<br />
This makes it possible, then, to reduce the vibrrtion<br />
transmission ratio to a value less lhan l.<br />
<strong>The</strong> skyhook darnper systcm thus allows considsritblc<br />
design frccdom for sctting thc dampinB rclio of activc<br />
control, (,, and that of the passivc damper, (r. In the<br />
Nissan hydraulic active suspension, these two damping<br />
ratios arc sct flt (z = 0.33 and (" = 0.42. Thcse values<br />
havc bcen $et so that thcy satisfy Eq. (5)<br />
F r e q ur n cy - de 1t e n d e nt dampi n g me c h u n i srn. I n thc c on -<br />
trol systcm shown in Figurc 3. thc prcssurc control valve<br />
functions as a damping clcmcnt against road surface<br />
inputs. As a result, the mechanism by whiclr thc susltcnsion<br />
gencratcs damping forcc is formed as shown in<br />
Figure 7(a). Using the equivalcnt modcl shown in (b) in<br />
thc tigure, thc transmissihility characteristic can be<br />
found as<br />
F2<br />
*, -f,,<br />
- r U . - _<br />
all+r<br />
W.T<br />
iCau+Ka<br />
.t(Cv+Ca)to+Ka<br />
(4)<br />
(5)<br />
(6)<br />
It is seen in Figure 7-(c) that the calculated result thus<br />
obtaincd agrccs wcll with the experimental data, which<br />
indicates that thc systcm has hccn ntodeled accuratcly.<br />
<strong>The</strong> equivalent dumping con$tant of this syslcln,<br />
Ceq(to), can be calculalcd with thc following exprcssion<br />
by letting H(tu) rcprcscnt thc right sidc of Eq. (6).<br />
Section 3: Technical Sessions<br />
(a) Denping System (b) gquivalent Model<br />
I<br />
q<br />
z 2-o<br />
I<br />
; .x<br />
!_ t.5<br />
5<br />
5<br />
€-r<br />
e<br />
n -<br />
€<br />
1.0<br />
.----::<br />
Bxp6ri-Ent<br />
H(o))<br />
'l<br />
fcalculation<br />
I ov:z. 5 kN s,/! |<br />
lca:2 0 kNs,/n I<br />
LKr= 31. 7 kNs,/o J<br />
....:<br />
(c) Cornparison between Experirnent andl Cafcufation<br />
Figure 7. Frequency-Dependent Damping Characteristics<br />
Ceg(ur) = lt1ro) | cos(lH(to))<br />
(7)<br />
Equation (7) is
13th lnternatlonel Technlaal Conference on Experlmental Safety Vehlcles<br />
6Passiv ({z=0.0r.{r=0.r) yibhtio6l Islrtlon<br />
' | '' rlrd;erfl<br />
_,. -1 - t -ft ti"e (f '-lo3as1<br />
c,_, i I F= frI"'''1r,.ri" I a.<br />
-/ _,[+\ i__---,7I\<br />
Spnr8 l&s lhlpfutr Inr6x d<br />
r- liiz:'xol.=a<br />
!\/lltl<br />
Flgure 8. comparison of Transmissibility<br />
lcat"rllionl<br />
a smaller value meilns better ride quality. <strong>The</strong> two<br />
indexes are given by the following equations.<br />
a =<br />
l.trl'tu I or = o,<br />
(8)<br />
F=+]'*,,*",0'<br />
(e)<br />
Figure 9 compares the performance of an active suspension<br />
and a passive suspension with respcct to thc indexes<br />
fl and F. With thc passivc suspension, a trade-off is<br />
required betwccn s and p. In contrast, the skyhook<br />
dampcr o[ the active suspension works to reduce rr and<br />
simultaneously the frequency-dcpendcnt damping mechanism<br />
is effectivc in reducing p. As a result, thc performance<br />
characteristic of thc active suspension shifts to<br />
the lower left region of Figure 9, surpassing the limits of<br />
the passive suspcnsion.<br />
Active<br />
I (, = o.rg, f*<br />
Passiv<br />
(r-0.17<br />
(r - 0.33<br />
(Stardard<br />
llEffect of<br />
Slqyhook hrp€r<br />
B: Effect of<br />
FrequencY<br />
Sensitivo DaDPing<br />
B<br />
olt, (,=o.u)<br />
F *u"-t<br />
Figure 9. lmprovemont of Ride Comfort (Calculation)<br />
Roll and Pitch Control<br />
Body roll resulting from the effect of lateral acceleration,<br />
such as what occurs during corncring. is supprcsscd<br />
by generating a counter roll moment, referred to here as<br />
798<br />
T H tb<br />
gl<br />
roll control. This is itccomplished by increasing thc<br />
hydraulic pressurc ilt thc oulside wheels of a turn and<br />
reducing it at the inside wheels so as to produce a<br />
counter force that is proportional to the output of lateral<br />
accelerometers.<br />
Pitch control is also effccted in the same way. A<br />
counter pitching momcnl is gcncratcd lhat is proportional<br />
to thc output of a longitudinal accelerometer. This works<br />
to suppress dive and squat motions during braking and<br />
rapid acceleration.<br />
Sincc roll and pitch control is used in combination<br />
with skyhook dampel control, the modcl shown in Figure<br />
l0 was prepared so thilt the enlire conlrol system could<br />
be analyzed. While this modcl focuses on roll, bounce<br />
and lateral molions. a similar ntodel can also he created<br />
for pitching.<br />
Vertical vibrrrion damplng Verticrl vlbrrtlon demplng<br />
Pressurecontrol<br />
YEIYe<br />
Lrietsl Eccclcratlon<br />
cohtrol gain -<br />
M: ychlcle mlsr<br />
L: uead<br />
J: mll mohenr of lnertie<br />
Cl tire corncrlng powrr/vchlcle ,pecd<br />
R": vefliCal rpdng ratc of rires<br />
Kr: laterrl stiffitess of tircs<br />
Figure 10. Analytical Model<br />
Roll conlrol respt)ns( in relatiott to trossu,intl inputs.<br />
Using the model in Figure 10, a crosswind input was<br />
applied to thc vchicle body in thc form of lr sine wave<br />
and the roll rate response was calculatcd. Thc calcuhtcd<br />
results arc shown in Figurc ll. Sincc this analysis did<br />
ntlt include yaw motion, the conditions wcrc slightly<br />
diffcrcnt from those of real-world driving. Nonetheless,<br />
thc rcsults clclrly indicatc tlrc cffccts oI roll control and<br />
skyhook damper control. It is seen that roll control is<br />
effective in suppressing body roll during corncring by<br />
counlcrbalancing the force of inertirr (centrifugal force),<br />
although it produces the opposite effect in relation to a<br />
crosswind. On the other hand, skyhook damper control<br />
works to suppress body roll even in a crosswind. It<br />
supprcsscs roll motion sufficiently to more than offset<br />
the incrcased body roll thilt is induccd when roll control<br />
is applied in a crosswind.<br />
Control of trunsienl sleer (:haratteilslics. Yaw stability<br />
gcncrally declines at higher driving speeds bccausc of<br />
the reduced gripping powcr o[ the tircs and the increased<br />
incrtial force ol'lhe vehicle owing to the occurrencc of
E<br />
Srs<br />
s t:<br />
'F ro<br />
bo<br />
E GI<br />
? 5<br />
d<br />
Active suspension<br />
(roll control)<br />
. Active suspension<br />
(roll control + skyhook oamper)<br />
0u Z A 6<br />
Hz<br />
Figure 11. Body Roll Response In Relatlon to Crosewind<br />
Input<br />
yaw motion. To overcome this problem, the Nissan<br />
hydraulic active suspension provides transient control<br />
over lateral load shifts that occur during roll control,<br />
which works to improve high-speed stability.<br />
<strong>The</strong> spccific method used is a very simple one in<br />
which the latcral accelerometer for the front wheels is<br />
installed aft of the lateral accelerometer for thc rear<br />
wheels. Typical experimental results obtained with this<br />
control procedure are shown in Figure 12. <strong>The</strong>se data are<br />
for a sudden lane changc that was executed at a speed of<br />
100 km/h. <strong>The</strong> notation s in the figure indicates the<br />
amount of change in transient steer chflractcristics and is<br />
given by<br />
n<br />
b<br />
T ^<br />
.g<br />
i<br />
f -zs<br />
25<br />
b<br />
- 0<br />
(10)<br />
where aW, is lhc lateral load shift at the front wheels<br />
and aW is the total lateral load shitt for both the front<br />
and rear wheels.<br />
-la<br />
25<br />
ilff'<br />
\+-*- Rol l/p I tch<br />
control<br />
g = lawl .t.{l -o.ot<br />
steef characterlstlc contro<br />
l._ r ____ l<br />
LWlth steer charact.ertsilc<br />
I th steer charag!!tlstlc contfol<br />
Wlthout steer characterlstlc<br />
c0ntr0l<br />
0 t 2 3 1 5<br />
Ttme (s)<br />
Flgure 12. Effec,ts of Steer Cheracteristic Control<br />
A comparison with the results obtained when the same<br />
lateral accelerometer was used for both the front and rear<br />
wheels indicates that the above-mentioned crlntrol procedure<br />
was effective in rcducing yaw rf,te overshoot.<br />
This is attributcd to the fact that it caused € to shift to<br />
Sectlon 3: Technlcal Sesslons<br />
the positive, i.e., understeer, side at the time of converEence.<br />
Characteristics of Mechanical Suspension and Sharing<br />
of Performance Load Between the 'l'wo Srrspensiots<br />
When a production vchicle is equipped with the<br />
hydraulic active suspension, it is necessary to return the<br />
mechanical suspension system to achieve a good match<br />
between the two systems. <strong>The</strong> procedure for matching<br />
active control and a mechanical suspension is outlincd in<br />
the flowchflrt in Figure 13.<br />
. Lll,l,le roll or pltch motlon<br />
. Llttle wheeltravel<br />
and llttle wheel camber<br />
W<br />
. Optlrnl?atlon 0l<br />
whee I camber<br />
accord Ing to stocl llBlc<br />
Llttle roll<br />
&<br />
. Small contrlbutlon ol<br />
roll understeer<br />
W<br />
. Optlnllzatlon of<br />
compllancd Steer<br />
ln relatlon to lateral<br />
lmprovrmcnt of hlgh-speed stabl | | ty<br />
wlthout changlng steer characterlstlCB<br />
Figure 13. Procedure for Matching Active Control and<br />
Itilechenical Suspension Character istics<br />
<strong>The</strong> aim of this matching procedure is to improvc yaw<br />
stability at high-speed without substantially altcring rhe<br />
steer characteristics.<br />
Thc proccdurc is explained here following the order in<br />
the flowchart. <strong>The</strong> effecrs of roll and pitch control are<br />
clarified in the first step. At the front end, the travel of<br />
thc outsidc whecls of a turn is reduced by the application<br />
of roll/pitch control. As a result, a larger effect is<br />
achieved by applying negative carnller according to the<br />
steer angle than by applying it on the bound side as has<br />
bccn done traditionally. At the rear, the reduction of roll<br />
motion makes it impossible to attain improved stability<br />
through thc usc o[ roll steer. Consequently, it is<br />
necessary to provide for a sufficiently large compliance<br />
steer chnracteristic.<br />
<strong>The</strong> second step concerns the optimization of the performance<br />
required of the mechanical suspension. <strong>The</strong><br />
third step indicates the directinn taken in tuning the<br />
mechanical suspcnsion. <strong>The</strong> fourth step indicatcs the<br />
final perfornrance objective, including the addition of<br />
transient steer characteristic control.<br />
In this example the mechanical suspension is adapted<br />
to active control in order to obtlrin the finrl perfrlrmance<br />
objective. Depending on the naturc of that objcctivc, it<br />
may be necessary to tune both thc flctivc control mclhod<br />
and thc charactcrislics of the mechanical suspension.<br />
799<br />
j,'l<br />
::<br />
.1
'tlth lntemettonet Technlcal Conference on Experlmental Setety Vehlcles<br />
Improvement in High-SPeed SafetY<br />
Contribution of Each Control Function to Performance<br />
Improvements<br />
Thc respective areas of vehicle performance that are<br />
improved by skyhook dampcr contrttl, frequcncy-dependent<br />
damping mechanism and roll/pitch control, the three<br />
major control features of the hydraulic active suspcnsion,<br />
are outlined in Figure 14.<br />
Skyhook damper control<br />
FrequencY -dependenI<br />
met<br />
R0ll/0ltcn control<br />
i\<br />
\\<br />
\]N<br />
4\ Tire<br />
--\<br />
Crosswlnd stablllty<br />
Flat vehicle attitude<br />
at hlqh speeo<br />
Ride comfort<br />
contact wlth<br />
clurinq cornerlnq<br />
H!gh-speed stablllty<br />
Flgure 14. Contribution of Each Control Function to<br />
lmproved Vehicle DYnamlcs<br />
Improvement in high-speed stability works to stubilize<br />
vehicle behavior following the execution of an emer'<br />
gency driving maneuver to avoid a forward obstacle<br />
when travcling at high speed. This improved stability<br />
helps to some extent to prevent accidents caused by<br />
unstable vehicle behavior resulling from the cxccution of<br />
such sudden driving operations by thc driver.<br />
Improved tire contact with the road surface during<br />
cornering can reduce the possibility of an accident due<br />
to swcrving by the vchiclc toward the road shoulder.<br />
Such vehicle behavior can occur as a rcsult of a<br />
rcduction in the cornering force of the tires while<br />
cornering on a rough road surfacc.<br />
Bctter crosswind slability and maintenance of a flat<br />
vehiclc attitude at high specd both increase thc capacity<br />
to stabilize vehicle behavior against external disturbances.<br />
Improvemcnts in these performance parilmetcrs<br />
help to reduce the driver's workload during high-speed<br />
driving.<br />
Improved ridc comfort resulting from a reduction in<br />
body vihration is effcctive in mitigating occupant fatigue<br />
especially during long trips.<br />
As those examples illustrate, the improvements in<br />
vehicle performance obtained with the hydraulic active<br />
suspension all help to stabilize vehiclc bchavior during<br />
high-speed driving and thus thcy serve to reducc the<br />
workload of the drivcr. In this way, they are effective in<br />
improving active safety at high speed.<br />
Steering Performance<br />
Sleer characteristics. Figure l5 compares the change<br />
in steer characteristics for an active suspension vehicle<br />
and one equipped with a mechanical suspension- Thc<br />
vehicles were gradually acceleratcd from a very low<br />
speed whilc turning in a circlc, l5 m in radius, at a fixed<br />
stccring wheel anglc. As was expcctcd, the active<br />
suspension vehicle displayed performance on a par with<br />
its mechanical suspension countcrpflrt'<br />
o<br />
E<br />
Fd<br />
2.5<br />
Figure 15. Steer Characteristlcs<br />
Frequency response ch(rrttcteristic. Figure l6 compares<br />
the yaw ratc response of thc two vehicles in rclation<br />
to a steering input of +30 dcgrees when traveling at<br />
a speed of 100 km/h. Thc active suspension vchicle<br />
shows a smallcr increase in the peak gain of thc yaw<br />
resonance frequency, indicating bctt.er yaw stability.<br />
vl<br />
\ 0 .<br />
c 0 .<br />
E<br />
fl0.<br />
(s<br />
L 0 ,<br />
3 G'<br />
ho<br />
[)<br />
E<br />
q)<br />
(,)<br />
(E<br />
-3<br />
-6<br />
-9<br />
-12<br />
-l 5<br />
-18<br />
0.4 0 6 0.8 1.0<br />
0.4<br />
0.7.<br />
0.4<br />
Conventional<br />
suspension<br />
v'--*\<br />
0.6<br />
l/t conventlonal<br />
'/<br />
suspenslon<br />
0.81,0<br />
0.6<br />
Figure 16. Frequency Response of Yaw Rate<br />
G<br />
Actlve suspenslon<br />
( v== | 00kn/h )<br />
2.0<br />
0.8<br />
3 0 1.0<br />
Hz<br />
Figure l7 shows a similar comparison for the roll rate<br />
response. <strong>The</strong> rcsults for the active suspension vchicle<br />
show effectivc suppression of body roll at a roll<br />
resonance frequcncy of I Hz. and phase improvement is<br />
also secn. While the reduction in thc stcady-state gain is<br />
attributed to the effcct r-rf roll control, the reduced gain
seen at the resonancc point is also due in part to the roll<br />
damping effect of the skyhook damper.<br />
^ 0500<br />
vt<br />
*' 0 100<br />
90<br />
6<br />
-/r t \<br />
t l ,1<br />
Conventionaliuspens<br />
lon<br />
;-fi 0.300<br />
\<br />
E 4- \ r<br />
Actlve suspenslon V<br />
r r r l<br />
0.200<br />
= 0100<br />
o<br />
E<br />
0.000<br />
0.4 0,6 0,8 t.0<br />
ho<br />
o<br />
rt<br />
dJ<br />
o<br />
(t'<br />
E<br />
3<br />
-3<br />
-6<br />
-9<br />
-\<br />
I<br />
'+. /<br />
$<br />
01 0.6 0.8 r.0 2.0 30 4.0<br />
Hz<br />
Figure 17. Frequency Response of Roll Rate<br />
Ride Comfofi and Tire Contact with Road Surface<br />
Figure 18 comprres the vertical vibration of the floor<br />
that was measured when the two vehicles were drivcn on<br />
a level road surface at a spccd of 100 km/h. <strong>The</strong> activc<br />
suspension car shows a lowcr vibration level in nearly<br />
every frequency range and the mersured data validate the<br />
calculated results prcsented in Figure L Thc reduced<br />
vibration level at sprung resonflnce frequencies of l*2<br />
Hz is attributed to the effect of skyhook damper control.<br />
At higher frequencies, the reduction is attributed to the<br />
effect of the frequency-dependent damping mechanism.<br />
<strong>The</strong>se results indicate that lhe Nissan hydraulic active<br />
suspension provides a $oft, pliant ride together wilh a<br />
flat. stable vehicle attitude.<br />
t o-'<br />
I<br />
E<br />
*\<br />
N,<br />
t<br />
:<br />
ut<br />
E ro<br />
V<br />
?.s<br />
3.0<br />
1.0<br />
Figure 18. Body Vibretion on e Levsl Road Surface<br />
4<br />
l l<br />
, l<br />
r l<br />
Figure 19 compares the body vibration that was<br />
measured in the two vehicles when they were driven at<br />
' :<br />
Sectlon 3: Techn ca, Sesston$<br />
high speed ovcr rn undulrting road surface which tends<br />
to causc sprung rcsonancc. Although this tigure shows<br />
only the results l'or vertical vibration, simillrr lcndcncics<br />
wcrc also observed for pitching. <strong>The</strong> low levcl of vibration<br />
sccn at low frequcncies where sprung resonance<br />
typically occurs indicutes thtt thcrc wits littlc change in<br />
tire contact with the rond surflce. This result clcarly<br />
shows the effectiveness of the active suspcnsion in<br />
improving the road surface colllilct of lhc tircs. In rcalworld<br />
driving, tire contact with the road surfacc hccomes<br />
an issue of concern during cornering. By ellectively<br />
suppressing body roll, the Nissan hydraulic uctive<br />
suspension assures sufficient suspension travel in the<br />
bound dircction flt thc outsidc wheels of a turn and this<br />
also contributes to improved tirc conlacl with the road<br />
surface.<br />
N<br />
i(<br />
; ooh<br />
:"<br />
A<br />
q<br />
c<br />
t<br />
o<br />
d<br />
o<br />
o<br />
q<br />
o<br />
d<br />
I<br />
r{<br />
o<br />
F<br />
l0-<br />
{ 5<br />
Figure 19. Body Vibration on an Undulate Road Surface<br />
Crosswind Smbility<br />
<strong>The</strong> results of a crosswind stability tcst indicatcd that<br />
thcre was r large differcnce in roll rales between the two<br />
vehicles, while virtually no dil'l'erence was seen in their<br />
yaw rates. Measured duta on the roll rates of the vehiclcs<br />
are given in Figure 20. l'hc r0sulls for thc active suspcn-<br />
?.6<br />
o<br />
E<br />
er 4<br />
g<br />
cl<br />
O r<br />
a<br />
Conventional Susp.<br />
iy'r- 4 Active Susp.<br />
Iy-l00kurtr]<br />
\--<br />
Active *u,P*n'ionA<br />
150<br />
Vehicle speed (km/h)<br />
Flgure 20. Crosswind Stability<br />
Hz<br />
:il I<br />
:<br />
j j<br />
' a<br />
it
13th lnternatlonal Technlcal Conlerence on ExPerlmental Sdtety Vehlcles<br />
sion vehicle show that skyhook dnmper control was<br />
noticeably effectivc in mitigating body roll even in a<br />
crosswind, as mentioned earlicr in 4.2.1. This damping<br />
effect contributcd to the improved crosswind stability<br />
seen for the activc suspension vehicle.<br />
Conclusion<br />
<strong>The</strong> results of theoretical analyses, simulations and<br />
experimentation show that the Nissan hydraulic activc<br />
suspcnsion mounted in the Infiniti Q45 achieves vchicle<br />
dynamic performance thal was previously unobtainable<br />
with conventional suspcnsions. This performance results<br />
from skyhook dampcr control, a frequency-dependent<br />
damping mechanism and roll/pitch control, the three<br />
major functional features of the suspension system, and<br />
from the good matching achieved between active control<br />
and the characteristics of the mechanical suspension.<br />
<strong>The</strong> improved performance itchicvcd with this stlspcnsion<br />
system works to stflbilize vehicle hehavior by minimizing<br />
attitude changes that can be induccd hy sudden<br />
driving mansuvers, crosswinds, road surface inputs or<br />
other changes in the driving environmcnt. Improvcd sla*<br />
bility, in turn, reduces the driver's workload undcr all<br />
sorts of driving conditions and thereby enhances active<br />
safety.<br />
s7-0-06<br />
Development of Tyre<br />
Roland Lucquiaud<br />
U.T.A.C.<br />
Checking Equipment<br />
Abstract<br />
In order to reduce the number of accidents due to tyre<br />
blow-outs on motorways, it has now become important<br />
to find technical solutions to improve road safety'<br />
Experience has shown that driving at high spccd on long<br />
distances with underinflated tyres may rcsult in a fatal<br />
blow-out. This may cven happen at an earlier stilge<br />
because tyres store many former aggressions. So we are<br />
currently developing methods and technical means to<br />
check the tyre prcssures and the good condition of tyre<br />
structures:<br />
' Tlre pressures using a slationary equipment localed<br />
outside the vehirle. This dcvice consists of a<br />
propclled mass ilnd a force transducer hitting the<br />
tyre tread. Parameters calculatcd from form and<br />
duration of thc delivered signal are related to<br />
inflation ptessure. <strong>The</strong> next step now consists in<br />
implementing lhe equipment where vehicles arc<br />
likely to stop for a short period of time (e.g. toll<br />
Eates).<br />
. <strong>The</strong> Eood condition of tyre structures (mainly the<br />
internal condition of the casing). A microphone set<br />
' close to a running tyre on a drum dclivers time and<br />
References<br />
l. Hedlick, J.K.,<br />
"Railway<br />
Vehicle Active Suspension,"<br />
Vehicle System Dynatnics, 10, (1981), p.267.<br />
2. Packer, M.B., "Activc Ridc Control-A Logical Stcp<br />
fronr Static Vehiclc Attitude Control," SAE papcr<br />
7800-s0.<br />
Wright, P.G. and Williams, D.A., "<strong>The</strong> Application<br />
of Activc Suspension to High Pcrlormance Road<br />
Vehicles," I Mcch E Paper, C 239, (l9lt4), p. 123.<br />
Kawarazaki, Y., et itl., "Dcvclopment<br />
of the Nissan<br />
Hydraulic Active Suspension," pre-print of SAE-<br />
Japan (in Japanese), 89? (1989-10).<br />
Yonekawa, T., "Vchicle Dynamics of Active Suspension<br />
Control," prc-print of SAE-Japan (in Japanese),<br />
90r (1990-s).<br />
Kamopp, D., "Active Damping in Road Vchicle Suspension<br />
Systcm," Vehicle Systcm Dynantics, 12,<br />
(1983), p.2et.<br />
Thompson, A.G, "Optimal 3.<br />
4.<br />
5.<br />
6.<br />
7.<br />
and Suboptimal Lincar<br />
Active Suspcnsion lbr Road Vchicles," Vehicle<br />
System Dynlntics, 13, (1984), p. 61.<br />
frequency signatures based on specific signal<br />
proccssing methods. A statistical analysis is then<br />
necessilry to correlate signaturc parameters and<br />
danger critcria for good and dantaged tyres.<br />
fntroduction<br />
A great amount of car accidents on motorways are due<br />
to tactors which differ from lho.se orr roads. namcly<br />
fatiguc, drowsiness, not taking account of bad weather<br />
conditions, lrlow-out of tyre$. Though driving on<br />
motorways is four or five timcs safer than driving or<br />
roads and tyre blow-outs ilrc responsiblc for mcrcly l07o<br />
o[ motorway car accidcnts, the aulomolivc industry hirs<br />
to carry out studies to reduce as far as possible the<br />
amount of accidcnts due to this.<br />
<strong>The</strong> blow out of a tyre could be linked to a mechanical<br />
failure of onc tyre. Howevcr, analysis often revcals that<br />
thc involved tyre was underinflated and rolling for a long<br />
time at high speed. Analysis may also rcveal that the<br />
involved tyre mily have stored former aggrcssiotts (when<br />
hitting the curb, or running over potholcs).<br />
Consequences of Driving with Tyres in Bad<br />
Conditions<br />
Driving with undcr-inflated tyres has the following<br />
consequences: it increases the car consumption, modifies
the road holding qualities (when braking or taking bcnds)<br />
at high speed without the driver's knowing. In this case,<br />
casing and tread plies arc submitted to an overheating,<br />
that may bring about the detachment of the tread pattern.<br />
On-Board Devices for Inflation Pressure<br />
Control<br />
<strong>The</strong>se devices are under development in order to<br />
control continuously thc inflation pressure of the four<br />
wheels and to warn the driver if a tyre is going flat<br />
(madc by Michelin, Bosch, Dunlop, Labinal, . . .). Thcse<br />
devices will only be supplied on "haut de gamme"<br />
vehicles on option within a few years.<br />
Checking the Inflation Pressure:<br />
0ur External Device<br />
<strong>The</strong> Principle<br />
Wc developed a measurement system that tllows to<br />
check the inflation pressure of tyres, ilt toll gates whcre<br />
vehicles still have to stop for a short timc. It rclics on<br />
the t-ollowing measurement principlc: a mass fitted with<br />
a force transducer is propelled and hits the tread pattern<br />
under the tyre. Form and duration of the delivered signal<br />
have to be analyzcd in order to estimate the inflution<br />
pressure: on figure l, wc can see that the longer the<br />
impact, thc less inflated is the tyre. But the impitct<br />
duration depends on the tyre ritructure (figure 2).<br />
Force (Nl<br />
TypE I Hxy 195/SE R 13<br />
15<br />
Time (ms)<br />
Figure 1. Inlluence of Inflation Pressute on the Shock<br />
Signal (for Two Extreme Prsssure Values)<br />
Data Processing<br />
Several parameters (shock cncrgy, asymntetric coefficient<br />
and kurtosis bascd on thc ?nd,3rd,4th statistical<br />
moments) can be calculated. For each tyre, a linear relation<br />
between parameters and air pressurs can bc lound<br />
(sce figure 3 for relation betwccn kurtosis and inflation<br />
pressure for two tyres). A prediction modcl for inflation<br />
pressurc has to be irnproved with a covariance analysis<br />
of a large amount of tyres. Our preliminar study shows<br />
that the model can't apply to all the tyres together. <strong>The</strong><br />
Section 3: Technica, Sessions<br />
Time (ms<br />
)<br />
Figure 2. Inf luence of Tyre Structure on the Shock Signal<br />
(lnflation Pressure = 2 bars, with Two Different Tyres:<br />
Michelin MXV 1S5/55R13 and Michelin X M+S 145H13)<br />
nrultiple corrclation cocl'l'icicnt irrcrcitscs wlrcn wc classify<br />
the tyres in lhrce clusscs: tyrcs for small rangc, ntedium<br />
range and high rrngc of passcngcr cars. <strong>The</strong> prediction<br />
modcl givcs morc reliable resulls for the first class<br />
which looks thc rnost honrogeneous: tyres with an overall<br />
width lowcr or cqual to 165 mrn and with an aspect rrtio<br />
belwccn 80 lnd 6-5).<br />
Kurtosi s I<br />
Curve 1: Michelin MXV with normal load.<br />
Curve 2; Same tyre with an additional load.<br />
Curve 3: Michelin X M+S. p = (JF'(t)dt)4F'(r)dr)'<br />
latJon Dressure (bars)<br />
Figuro 3. Kurtosie Coefflclent Calculated for Different<br />
Inflation Pressure$, for Two Different Tyres<br />
<strong>The</strong> Devite<br />
<strong>The</strong> next step is to design the device that could test flt<br />
once one rrxlc of passcnger cars, taking into ilccount<br />
diffcrent aspects, such as cflr pilsscngers sii[ety and thc<br />
vchicle's wheels pcrsition. For this, all the lnobile parts<br />
have to bc implenrcltted under thc ground; thc guns containing<br />
lhc cquipped nrass havc to movc quickly lcl-t or<br />
803<br />
+
l3th lnternetlonal Technlcal Canference on Experlmental Satety Vehicles<br />
right according to vehicle position and gauge (figure 4).<br />
This dcvicc will allow us to improve our prediction<br />
modcl in order to obtain a better accurilry of inflation<br />
prcssure estimation. Furthcrmorc, we hilvc to study the<br />
influence of othcr paramclcrs, such as tyrc tcmpcrirture,<br />
ambicnt tcmperature, tread wear . . . .<br />
Figure 4. Sketch of the Checking Equipment lor Inllation<br />
Pressure<br />
Checking the Tyre Structure<br />
Aho ut Te c hnit: al C he t: ki nB<br />
A complctc invcstigation of tyrc conditions must bc<br />
performed wilh the control of thc trcad wear and an<br />
internal control of the casing. Thc irrcgular wear of' the<br />
tread is duc to shock absorbcrs, wheel trrin, stccring or<br />
braking parts that nccd to bc rcpaircd. But, il appcflrs to<br />
bc morc difficult to asscss whcther shocks on thc casing<br />
plies or breakers are serious 0r not with0ut rcmoving thc<br />
tyre. It is also possihle to detect inside the casing (by<br />
mottlings on the sidewrll) when a vehicle has been<br />
drivcn with undcr inflatcd typc for a long timc.<br />
Our Method<br />
In order to detect the faults of tyres that can't be<br />
detected by a visual inspection, we investigated on a<br />
method using acoustics means. <strong>The</strong> principle is similar<br />
to the one applied for fault detections in rotating<br />
machines (gears and bearing of gerrrboxes, blades of funs<br />
or turbines). We hitve to analyze the sound prcssurc of<br />
a microphone closed to thc tyre running on a drum. On<br />
figure 5, a fault can be revealed on a time signature.<br />
<strong>The</strong>se time signatures are ohtained by a "conditioned"<br />
avcraging: cach signaturc last:i onc tyrc rcvolution and is<br />
averaged synchronous with each revolution in ordcr to<br />
extract the tyre-pcriodic signal. Thc spcctral signrturcs<br />
of the sound pressure signal show many pcaks at harmonics<br />
of the revolution frequency. With these spectral<br />
data, wc nccd to apply spccific signirl proccssing<br />
methods (cepstrum analysis, Hilhert transtirrnr) that<br />
allow us to come back to the time domain. <strong>The</strong>se<br />
mcthods may hclp diagnosc the periodic faults on il tyre.<br />
Develttpmenl Work<br />
In ordcr to improvc thc analysis, wc havc to fill in a<br />
bank of signaturcs ol'tyrcs, somc with well-known laults<br />
and some wilhout any faults. <strong>The</strong> study of the signatures<br />
804<br />
-{ .0<br />
Ambl i tude (Pa )<br />
II<br />
I<br />
I r / l<br />
i--'---** **1<br />
I<br />
I<br />
I<br />
-' -'-'--' - - -- '<br />
i.'<br />
q t . | | t t l<br />
'i<br />
-i*"-**-"-1"'<br />
r I<br />
i ; local fauljt I<br />
i l l r<br />
r l<br />
0,00 0. e0 0. 40 0.60 0 .80 t .00<br />
Tryre revolution<br />
Figure 5. Time Signature for a Tyre Without Any Fautt<br />
(60 km/h, Inflation Pressure 4 Bars)<br />
-s.0<br />
-e!i.0<br />
-:8.0<br />
-45.0<br />
0.0 5.0 to.o ts.o 20.0 25.0<br />
Rotatlon orders<br />
Figure 6. Spectral Signature for a Tyre Without Any Fault<br />
(60 km/h, Inflation Pressure 4 Bars)<br />
content requires knowledge about how tyrcs are mflnufacturcd<br />
in nost cascs rrnd about thc noisc gcncration<br />
mechitnisms. We also hilvc to study the influence of<br />
rolling conrlitions and find thc trest (for inflation<br />
prcssurc. rcvolutiolr spccd).<br />
Acknowledgrnents<br />
<strong>The</strong> author gratcl'ully acknowledges the trclp oi<br />
ASSECAR (Associllion Sccuritc Autoroute) for the<br />
dcvcloprncnt o[ tlrc inflation prcssurc chccking cquipmenl,<br />
and the suppurl of SERT (Scrvice des Etudes de la<br />
Rcchcrche ct dc la Tcchnologic du Ministsrc de<br />
I'Equipement, du Logetnent, des Transports et de<br />
I'Espace) for the investigations on both nrelhods.<br />
References<br />
l. R. Lucquiaud: Sous gonfllge des pneumatic;ues.<br />
Rapport TJTAC 90/138-5. Novemtrre 1990.<br />
2. R. I,ucquiitud: Controle de I'dtat interne des pneumatiqucs.<br />
Rapport LITAC 90/1986. Novcmbrc I990.<br />
3. ASSECAR: Sous gonflagc dcs pncumiltiquesenscigncrncnts<br />
i tircr de I'opiration. Plcin d'Air iti<br />
1985 Fevrier I 986.
5.<br />
7.<br />
M. Scholz: "Fahrzeugreifen:<br />
Ungleichfdrmigkeiten<br />
an Luftreifen." Tcil I + Tell 2 - F + K ll/198a pp<br />
30-32 F + K l2l1984 pp 34-36.<br />
"Les<br />
causcs d'usure et de ddtirioration prCmaturCcs<br />
des pncus." Lc rclais - Total. Mai 1985 et Juin 1985.<br />
J,F. Gaillochct:<br />
"Mithodes de surveillance de I'dtrt<br />
micanique des machines ilu moycn dc I'analyse des<br />
vibrations." Note interne Cetim. Juillct 1979.<br />
P. Coudray;<br />
"Survcillancc<br />
des machines par analyse<br />
de vibrations. Application aux rdducteurs h engre-<br />
iiJJtooout th; Averaee Driver in a Critical Situation?<br />
Can He Really Be Helped by Primary Safety Improvements?<br />
Alain Priez<br />
Institut de Recherche Anatamo-Chinrrgical et<br />
de Biomdcanique Appliqude<br />
Claire Petit<br />
Institut de Recherche Biomdcanique et<br />
Accidentologique<br />
Bruno Gu€zard, Lionel Boulommier<br />
Association d'Aide I la Recherche<br />
intdressant la Mddecine du Travail<br />
Andrd Dittmar, Alain Delhomme<br />
Laoratoire de <strong>The</strong>rmordgulation CNRS URA<br />
Evelyne Vernet-Maury<br />
Universitd C. Bernard<br />
Edwidge Pailhous<br />
Psychologist, 82 bd. Buzenval, Paris<br />
Jean-Yves Foret-Bruno, Claude Tarriere<br />
Renault France<br />
Abstract<br />
Since primary safcty is the unique possihility to<br />
protect automobilists in l/2 of the crashcs. it necds lo<br />
{uantify thc clficiency of thesc systems. Tho aulhors<br />
consider that a primary safety systcm is efficicnt only il'<br />
it avoids dead or injurcd pcople: Both the driver and lhe<br />
systern have to be trailed at thc samc timc. Thc ABS has<br />
recently been studicd in this airn through a 100-drivers<br />
experiment. Prcliminary results are shown. Allhough thc<br />
ABS is fanrous, it appears lhat nrost drivcrs don't know<br />
how it works and misused it.<br />
Introduction<br />
In 1990, road accidents in France resulted in 10,289<br />
deaths (6,295 automobilist deaths). Despite all the<br />
improvcmcnts which it is possible to milke to diffcrcnt<br />
restraint systems (assuming thflt cvcryone uscs these<br />
dcvices), and taking into ilccount all lhe intprovctncnts in<br />
vehicle structural rcinlorcement still possible, in at lcasl<br />
L<br />
9.<br />
Section 3: Technlcal Sessions<br />
nages.- Ingenieur de l'Automobile. Janvier-Fevrier<br />
1983. n" I, pp 60-65.<br />
G. Sapy:<br />
"Unc applicalion du traitement numdriquc<br />
des signaux au diagnostic vibratoirc de panne: la<br />
ddtection des ruptures d'aubcs de turbincs."<br />
Automatisnre toms xx, no 10, Octobre I975. pp 392-<br />
395.<br />
R.B. Randall:<br />
"Cepstrum<br />
anllysis and gcarbox lhult<br />
diagnostic." Bruel & Kjucr application. Note 233-iiO.<br />
SlVo of the cases, impact scvcrity is so greal lhfll it<br />
seems lo lrc outsidc lhc rcallrt ol currenl scconditry safcty<br />
technical capltrilitics lnd ccununtic pr-rssihilitics<br />
(Thonras.89). Tlris bcirrg thc casc, thcn in ttrorc thln l/2<br />
of accidents. thc only solution is primary safcty and<br />
accident avoidlncc.<br />
Accidcnt lvoidrnce $y$tems are already available in<br />
vehicles (anti-lock hraking systclns (ABS), controllcd<br />
suspension systenls, . . .) or arc being studied by different<br />
car or fittings manuftcturcrs. lhcy'rc even being<br />
studied within the framcwork o[ cxtensive internationrl<br />
research progrilms (PROMETHEIJS, DRIVE). Thcsc<br />
dcvices are going lo allow il bcltcr rnanagemenl of sontc<br />
situation reaching thc lirnits of the vehicle potcntial.<br />
maybe evcn trill-l'ic rulcs. Yct such changes in thc wiry of<br />
driving arc uscf ul only if lhe syslcm's cfficicncy is real.<br />
Need to Evaluate Primary Safety Systern<br />
Efficiency<br />
Prinrary snfety system cfficiency can be evntutted in<br />
lernrs of pcrforrnance improvcntcnt. It is possiblc lo<br />
nlcasure in a prccisc wily lhc irnprovetnents to roitd<br />
slflbilily or vchiclc braking obtaincd l'rottt the use oi such<br />
a dcvicc. Howcvcr, itnprovcmcrtts in vchiclc potential do<br />
not ncccssillily corrcspoltd lo ;tctultl intpt-ovcmcltls itt<br />
Occupilnt sa[cty.<br />
Anothcr nre thod of approach is to cvaluate thc cfficicncy<br />
of n primary .srfely syslcm in lcrrli$ of accidents<br />
clusing injury which have bccn lrvoidcd or lives saved<br />
duc to the use of thc systcIIl. Thc information thus<br />
obtainecl is dircctly usclble to show lhc bcrrc[its possible<br />
from the generalized usc ol'lhc given systcn.<br />
Howcvcr, lhis approach is much ntore difficult to<br />
carry out. In frct, in order to havc rcliable statiliticnl<br />
dflta, it is ncccsslry to test the printary safety systcm on<br />
a large scalc, which rlcilnri hrving a largc ntrnthcr of<br />
vehicles equipped wilh the system artd carrying out<br />
measurcrncnts over a sufficiency long pcriod of time lnd<br />
flcross r sufficicnlly vilsl geographictl arcl. Thus. thc<br />
first drawlllck to such ittt itltJtrttltclt is thlt informalion is<br />
805<br />
-i: i<br />
.i<br />
-*<br />
':
13th lntematlonal Technlcal Conference on Expertmentat Satety Vehlcles<br />
not available immediately but rather after a long delay<br />
which hinders the development of the system and improvement<br />
of its performance.<br />
<strong>The</strong> other drawback is the very complexity of carrying<br />
out such an approach. <strong>The</strong> study cannot be carried out if<br />
the data collected at the scene of an accident is not<br />
precise or sufficient enough. Collecting such precise and<br />
adequate data means having people trained in gathering<br />
such data at the scene of an accident. As well, the givcn<br />
device's effect can only be determined by dctcrmining<br />
the cause of the accident, which is long and tricky work<br />
as it is susceptible to the injured or witness account<br />
reliability and to the intcrpretation of those doing the<br />
study. Lastly, accident study cannot be complete. In<br />
1990, the French National Gendarmerie recordcd 59,799<br />
road accidents involving injurie.s. To this already high<br />
figure, it is necessary to add the accidents recorded by<br />
the National Police: in other words. the amount of data<br />
involved is considcrablc. Accidents resulting in only<br />
damage to propcrty are not recorded although the safety<br />
device may have been responsible for making it possible<br />
to avoid injury in such accidents. In this case, only the<br />
damage to property is regrettcd, while perhaps the accident<br />
itself could have becn avoided! Evcn insurance<br />
companies can only count the fatal, injury provoking or<br />
property damaging accidcnts, thcy cannot tflke into<br />
account<br />
"almost accidents" which every driver experiences<br />
at sometime. and which were avoided thanks to the<br />
safety dcvice which nccds to be cvaluated. If the nonanalyzed<br />
data in one ycar is difficult to interpret, it is<br />
possible to study the evolution of this data from year to<br />
year and compare the results from year to year.<br />
If this approach involves complex implementation, it<br />
is the only one which can potentially quantify the gain in<br />
terms of lives saved through the use of a given device.<br />
A last approach consists of evaluating the cfficiency<br />
of a device during a test whcre thc pcrformance of the<br />
driver-vehicle pair is studied. This approach does not<br />
allow the direct quantification of the gain in terms of<br />
lives saved, but it does considcrably simplily thc study.<br />
<strong>The</strong> fact that it consists of a test situation, means that the<br />
same accidcnt can be duplicatcd as many times as necessary,<br />
thus obtaining data from perfectly comparable<br />
circumstances. <strong>The</strong> number of experiments being known,<br />
it is very easy to measure the numher of accidents<br />
avoided or involving low levcl impact. Last of all, the<br />
driver and the vehicle can be equipped with captors<br />
thereby simplifying considcrably the collection of dala<br />
concerning the pre-collision phase, in comparison to the<br />
collection of post-accident data. If the collection of<br />
statistically reliable data is easier using this method, the<br />
population studicd will always remain limited as will the<br />
accidcnt provoking configurations looked at. Only estimates<br />
will be possible from the situations tcstcd.<br />
Evaluation of Anti-lock Braking System<br />
Efficiency<br />
<strong>The</strong> anti-lock braking system is the most promising<br />
primary safety system which has bccn put into general<br />
use in vehicles over the last l0 years. When it came out,<br />
ccrtain insurance cornpanies offered lower insurance<br />
premiums for vehicles cquipped with the ABS systcm.<br />
Aftcr a number of yeius, these same insurance companies<br />
are now cancelling this advantage sincc equipped<br />
vchicles do not seem to be less involvcd in accidents<br />
than unequipped vehicles. <strong>The</strong> advantagc in having an<br />
ABS braking $y$tem is howevcr obvious. It allows<br />
vehicle control while braking through optimal use of<br />
adherence conditions and rcduces braking distance to a<br />
minimum in all situations. So, while the efficiency of the<br />
ABS system is clear, its road efficicncy remains to be<br />
seen, at least in terms of reducing the numbcr of accidcnts<br />
and accident victims.<br />
A number of studies huve lreen carried out to nleasurc<br />
the cfficiency of the ABS system. Its usefulness was<br />
demonstrated on a test course while braking in a curve<br />
(Lechncr ct al., t989). Non-profcssional drivers were to<br />
brakc violently upon passing a marker placed at the beginning<br />
of a curve while driving at the instructed spccd<br />
of 75 km/h. <strong>The</strong> increase in steering control is evidcnt:<br />
most braking with the ABS system mainlained to the<br />
vehiclc's trajectory and thc vehiclc was stopped without<br />
leaving the road. This tendency was revcrscd when braking<br />
was carried out under the same test conditions without<br />
an ABS system. However, even if thc drivcrs wcre<br />
not professionals, the fact that drivers were requested to<br />
brake upon passing a miuker took away the element of<br />
surprise and renders this test closer to il mere vehicle<br />
pcrlormance test. Driver participation is in fact con'<br />
ditioned by the experimental circumstances, which limit<br />
the effect of the driver-vehicle interaction. In a study of<br />
drivers' emergency millloeuvres during a critical inl.crsection<br />
situation, using a Daimler-Benz simulator,<br />
(Malaterre and Lechner, 1989; Lechner and Malatcrre,<br />
1990) the efficiency of fhe ABS system was not clircctly<br />
measured (the sirnulator was not cquippcd with the ABS<br />
system). However, the possible gain from such a systcm<br />
was extrapolated as a function of the mcasures camied<br />
out. 20 7o of the accidents were avoided without thc ABS<br />
system. With an ABS system, an additional l4 7a of the<br />
accidents would have been avoided and the consequences<br />
of the accidents would have been lessencd in 407o ol the<br />
remaining cases. <strong>The</strong> difficulty in duplicating, with a<br />
simulator, the behavior of a vehicle equipped with the<br />
ABS system limited this study to making projections<br />
about the cfficicncy of thc ABS systcm. Recent progress<br />
in simulation modcls should improve simulator credibilitv.
Experimental Procedures<br />
<strong>The</strong> above two examples reveat the need to carry out<br />
an ABS system study under real driving conditions. Of<br />
the 37,972 accidenrs leading to injury involving at least<br />
one car which occurred on French roads in 1990. 13.749<br />
were two-car accidents. Of these, 3,243 took place outside<br />
of city limits and at an intersection. This accidcnt<br />
configuration, which corresponds to a quartcr of thc accidents<br />
involving two vehicles, seems typical o[ a configuration<br />
wherc the ABS system would have considerable<br />
positive effect on safety. <strong>The</strong> study described in this<br />
article is based on this accident type.<br />
100 volunteer subjects were recruited from among<br />
Renault personncl. Thcy wcrc sclected with the help of<br />
psychometric tests in ordcr to cvirluirte their level of<br />
emotionality (Eyscnck pcrsonality tcst and the Stroop<br />
stress test). All those chosen had a driver's license but<br />
the length of time they had it varied. None of them were<br />
professional drivers. Four groups of 25 subjects were<br />
formed:<br />
' Group I used a car without an ABS system<br />
. Group 2 used a car equipped with an ABS system<br />
but were not ilware of this<br />
. Group 3 used a car equipped with an ABS system<br />
and were aware of this<br />
. Group 4 used a car equipped with an ABS system<br />
and had attended a half-day training in its usc. This<br />
training consisted of a theoretical pirrt explaining the<br />
objectivc and functioning of the ABS system, as<br />
well as a practical part involving dcmonstrations and<br />
avoidance exercises. This training took place two<br />
months before tcsting.<br />
Dividing up of the subjects was carried out based on<br />
the psychometric test results so as to obtain homogeneous<br />
groups in terms of age, lcngth of time in<br />
possession of a driver's license and cmotionality. <strong>The</strong><br />
fact that the test population was recruitcd from a sample<br />
of the working population lead to the under-represcntfltion<br />
of older people. However 10o/a of the drivers<br />
involved in this kind of situation were represented.<br />
<strong>The</strong> subjects were informed that they wcrc trking part<br />
in a study on primary safety and that their behrvior, as<br />
well irs that of the car, would be recorded during a<br />
driving run on a circuit which could present "critical<br />
situations." <strong>The</strong> car used was a Renlult 25 TXI. In rhe<br />
cars used by Group I subjccts, the ABS sysrem was disconnected<br />
and braking was therefore of thc normal sort.<br />
<strong>The</strong> course was a closed circuit made up of connecting<br />
roads, parts of the circuit track and a two-lane road (7 m<br />
wide) delimited by cones placed in an open area. <strong>The</strong><br />
course crossed a number of intersections, of which two<br />
were in lhe part of the course delimited by cones. At<br />
these two intersections, Renault l9 cars were stopped flt<br />
stop signs with a driver at the wheel. Subject visibility<br />
was restricted by safe, artificial (polystyrcne) walls<br />
which made it impossiblc to see the stopped Rcnault l9s,<br />
Secfion 3: Technlcal Sessrons<br />
up unlil lhc lrst minute, ai these two inrersections. <strong>The</strong><br />
other intersections can be relatively open or masked by<br />
vcgetation.<br />
<strong>The</strong> subject generally completed three runs of the<br />
coursc to become familiur with the car ilnd the course.<br />
<strong>The</strong> number of runs can be varied so that those subjects<br />
waiting cannot figure out the length of the experiment.<br />
<strong>The</strong> course was new to each subject at the beginning of<br />
the tcst and the subjects waiting had no crlnlact with<br />
tho$e who had already conrpletcd thc tcst. Onc run lastcd<br />
4 minutcs and thc total lcngth of time to complete the<br />
test was about l2 minutes. <strong>The</strong> instructed spced was 100<br />
km/h on slraightaways and 80 kmfir on curvcs. An<br />
experimenter, always thc s:rrnc, wc$ nexl to thc subjcct<br />
in the car in order to givc spccd and driving instructions<br />
and to verify if these instructions wcrc carricd out. <strong>The</strong><br />
experimenter also ensured thc safcty of thc subjcct by<br />
correcting any manoeuvres thal could bc ihngcrous.<br />
During the last run, thc Renault l9 positioncd to the<br />
right of thc sccond intcrscction was replaced by an<br />
inllated dummy car having the s{tme features as a<br />
Rcnault 19. Tlrc subjcct's cirr pirsscd in front of tn<br />
optical bcarn which triggered a synchronizirtion signirl<br />
which releascd thc obsttcle. <strong>The</strong> walls concclrling rhc<br />
intcrscction did not allow the subjects to see the obstacle<br />
until it pulled out into their lane. At this moment, given<br />
the speed of 100 km/h and il mcan rcaction timc cstimated<br />
at 0.8 seconds, the braking distance was l5 meters<br />
too short to avoid the obstacle. <strong>The</strong> average speed of the<br />
subject's car when it arrived at thc obstaclc was 40-50<br />
km/h. <strong>The</strong> obsmcle car crossed half of the intersection<br />
and then stopped. <strong>The</strong> left lane was free, allowing the<br />
subject's car to pirss. This siturtion being very difficult,<br />
the first avoidancc rcaction was thc only chancc to avoid<br />
the obstacle.<br />
<strong>The</strong> airn of the study was to cvaluate the ABS system's<br />
efficicncy considcring thc drivcr's usc of it. To do<br />
this, a number o[ paranreters were recorded from the car<br />
and from the subject. <strong>The</strong>se were the following:<br />
. From the car (16 paranrctcrs)<br />
- speed of each wheel<br />
- the ABS system's solenoid valve setting<br />
- steering wheel angle<br />
- longitudinrrl and transversal acceleration<br />
- brake pedal displacelnent<br />
- actions carried out on the accelerator, clutch and<br />
brake<br />
- actions carried out on the emergency brake<br />
- enginc spccd (to dctcrminc shifting)<br />
- obstaclc cilr slflrt up synchronizltion (photoclectric<br />
cclls)<br />
- sync signals<br />
. From the subject (12 parnmeters)<br />
- capillary flow<br />
- skin potcntial<br />
- skin rcsistance<br />
- skin temperature<br />
807<br />
::<br />
i1<br />
.l<br />
.:<br />
,.il<br />
':,i<br />
-;l<br />
'!<br />
'
lilth lntematlonal Technlcal Conlerence on Experlmentel Setety Vehlcles<br />
- breathing rate<br />
- hcart rate<br />
- biceps brachialii and finger flexor etectromyogrf,ms<br />
(EM6)<br />
- horizontal and vertical electro-occulogram (EOG)<br />
- a micro-camera attached to the subject's right<br />
forehead to record his/her field of vision<br />
' a vidco camera attachcd to the right-hand comer of<br />
the dashboard to film the subjcct's upper body<br />
during the experiment<br />
<strong>The</strong> measurements were recorded throughout the entire<br />
experiment.<br />
<strong>The</strong> first six measurements collected from the subjcct<br />
were designed to measurc his/her concentration and<br />
stress level. All changcs in concentration, even a simple<br />
mcntal computation, lead to neurophysiological changes.<br />
Thc first four measurements were collected from the<br />
palm of the left hand. <strong>The</strong> captors were placed in such a<br />
wfly so as not to hamper driving. <strong>The</strong> breathing rate wils<br />
constantly measurcd by using a temperature sending unit<br />
placed under the nose. <strong>The</strong>se measuremcnt systems were<br />
developed by the URA CNRS l34l Lahoratory of<br />
<strong>The</strong>rmoregulfltion (Dittmar ct al., 1985).<br />
<strong>The</strong> EMG meilsured on thc arm was designed to<br />
measure the subject's force and clutch on thc whcel. <strong>The</strong><br />
EOC and the micro-cameril were uscd to cvaluatc where<br />
the subject was looking.<br />
Furthermore, in order to examine the overall<br />
emotionality level of thc subjects confronted with such<br />
a situation, all subjects fillcd out a self-evaluation<br />
questionnaire (ASTA test) before and after undergoing<br />
testing.<br />
<strong>The</strong> aim of all these measurcmcnts was to objectify<br />
the subject's capacity to use thc potential of the vehicle<br />
drivcn. <strong>The</strong> different tests made it possiblc to obtain<br />
homogeneous Broups in terms of emotionality and to<br />
dctcrnrinc the emotional state of each subject bcforc and<br />
after thc expcrimcnt. <strong>The</strong> first two runs establishcd thc<br />
rcfcrcnce level for the parilmeters collcctcd lrom the<br />
subject and detcrmincd the way the suhject deillt with an<br />
intersection and his reactions in an ctrtcrgency situation.<br />
Results<br />
Testing was carried out during the summer of 1991.<br />
<strong>The</strong>refore, only preliminary results from 87 subjects will<br />
be presented here.<br />
Influence of Group<br />
<strong>The</strong> population studied was divided into four groups<br />
as a function of the information givcn to thc subjects<br />
about the ABS braking system. <strong>The</strong> ages and scnsitivity<br />
to stress of group mcmbcrs were homogeneous across<br />
groups:<br />
. Croup l: the ABS braking system was disconnected<br />
("normal" braking)<br />
. Group 2: the car was equipped with an ABS system<br />
but the driver wasn't aware of it<br />
808<br />
. Group 3: the car was equippcd with an ABS systsm<br />
and the driver was aware of this<br />
. Group 4: the car was equipped with an ABS sy$tem<br />
and thc drivcr had training<br />
Rcsults by group arc givcn in Table l.<br />
Table 1<br />
ErcuD I Enrun 2 muu 3<br />
Sumessfullv avoided o% 2t.8 % 11.7 Vo 29.2%<br />
Tricd to avoid 19-l 9o 30.4 E 23.5 % 50 pk<br />
BmldnE oillv 56.9 9o 3E.E'ft' 46.8 % 20.1\ Vo<br />
No anemDt 4Va 9% 1Z Eo 0E<br />
<strong>The</strong> term --tried to avoid" refers to subjects who<br />
carried out a complex avoidance manoeuvre, thilt is to<br />
say brnking and stccring whccl movcmcn(. Evcn if thcy<br />
did not succccd, such a tnanoeuvre was necessary to<br />
avoid thc obstaclc. In thc cose of those that tried to<br />
avoid the obstrclc, intprcl ntight have bccn less violent<br />
but data analysis to dulo has nol gonc so far as to lct us<br />
break this down further.<br />
If we want to look more closely at driver behavior and<br />
his/her ability to u$c all thc ABS systcnt's potcntial in<br />
thc given situation. il is ncccssary to look at the l'irst two<br />
lines of Tahle l. Thc efficicncy of the ABS systcm is<br />
demonstrated in the results obtaincd wilh group I for<br />
none of these subjccts, who wcrc driving cars not<br />
cquippcd with lhc ABS system, succeeded in avoiding<br />
thc obstilclc.<br />
40 to 50 7o of subjccts attempted (successfully or not)<br />
to avoid thc obstacle by turning the wheel. This percentage<br />
rcaches tlO 7o for those in group 4 who attcnded a<br />
half-day training in avoidancc manoeuvrcs.<br />
<strong>The</strong> test was judged realistic by all of the $ubjects.<br />
Only a few subjects judgcd the obstacle insufficicntly<br />
realistic. It should be notcd that nonc of thc subjccts who<br />
judged the obstacle insufiiciently rcalistic succccdcd in<br />
avoiding it and all of them had a very belated reaction.<br />
It is difficult. givcn thc limitcd drta analyscs having<br />
been carricd out to date. lo determine if the statement<br />
that the obstacle was insul'ficicntly rcalistic is duc to the<br />
real opinion of the subject, or is an attempt on the<br />
subjcct's pflrt lo cxcuse his bad reaction.<br />
Influenee of Age<br />
If we study the population as a whole, age does not<br />
seem to effect results. <strong>The</strong> averilge age of subjccts who<br />
avoided the obstaclc is 32.5 (+ 7.3 years), the average<br />
age of thosc who carried out a complex avoidance<br />
manoeuvre is 30.1 (+ 6.-5 years), and that of thosc who<br />
tricd nothing is 31.7 (+ 7.3 years). It is however interesting<br />
to study this point in more detail by breaking<br />
down the population as a functiott of age (see Tablc 2).<br />
Subjects between the ages of 26 and 36 have the highest<br />
succcss ratc. Approximately 60 o/o of subjects over 26<br />
completed a proper manoeuvre, while only 45 7o of lhose<br />
under 26 and over 37 contplcted a proper milnoeuvre.
Table 2<br />
< 26 yean old 26 to 36 ycars<br />
old 37 to 47 yeus old<br />
Successfullv avoided 9.r % 21.8 Vo I 5.8 7o<br />
Tried to avoid 36.4 % 39.t % 31.6 %<br />
Bnkins onlv 5O 7o 39.1 % 47.4 7a<br />
N() arteflDt 4.5 % o% 5.2 %<br />
None of the subjects in the study were ovcr 47 yets<br />
old. This definitely results in a skewed study as 29 7o of<br />
French drivcrs on the roads are over this age. As well<br />
they make up 37 Vo o[ those involved in this type of<br />
accident and 50.5 7o of those presqmed resprinsible for<br />
such accidents. This ovcr 47 agc group arc nrainly the<br />
drivcrs of thc car which cuts across the road, represented<br />
in this study by the obstacle. However, considering only<br />
thc drivers who are not re$pon.sible, the Renault 25<br />
drivers, the test population covers more than<br />
'10 o/o of the<br />
age groups concerned.<br />
Length of Driving Experience<br />
<strong>The</strong> amount of driving cxperience can be measured by<br />
the number of years the person has had his/her driver's<br />
license. Subjects who avoided the obstacle had their<br />
license, on the irverage, for I3.7 ycars (+ 6.4 ycars).<br />
Those who carried out an avoidirnce milnoeuvre had it.<br />
on the average, for ll.9 years (+ 6.8 years). Those who<br />
did not attempt an avoidance milnoeuvre had it for 12.8<br />
years on the average (+ 7.3 ycars). <strong>The</strong>sc diflcrcnccs are<br />
not signiticant. A detailed breakdown is given in Table<br />
3.<br />
Table 3<br />
< l0 veus l0 I 20 vem 20 ii 30 ycars<br />
Successfully avoided 15.5 % 20E 17.'1 Vo<br />
Tried to avoid 35.6 % 40E 294 %<br />
llrukiils onlv 46.7 % 20.8 tk 52.9 7o<br />
No attemDt 7.2
lStn hwrnatlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
the ABS braking system during their first try at sff;ight<br />
line --emergency"<br />
braking. AII subjects had to try again<br />
at least once in order to succeed (for each of the two<br />
cxercises, the subject continued trying until s/he<br />
succeeded).<br />
<strong>The</strong> fact that setting up such a short training is<br />
relatively simple, increases the interest in doing so.<br />
Moreover,4 of the subjects owned cars cquippcd with an<br />
ABS system. <strong>The</strong>y were placed in the first group (2<br />
subjects), the third group (l subject) and the fourth<br />
group (1 subject). Even thought this number is too small<br />
to be statistically significant, the first three subjects did<br />
not try to turn the wheel during the test, only the subject<br />
in the fourth group carricd out the proper manoeuvre<br />
(and avoided the obstacle). Despite the fact that thcir use<br />
o[ the ABS system was not good, these subjccts fclt<br />
more confident bccause their car was equipped with the<br />
system.<br />
It may be initially surprising to note the results of thc<br />
third group, which was informcd that their vehicle wlts<br />
equipped with an ABS systcm, were not a$ good as the<br />
results from group 2, which was not informcd thcir<br />
vehicle was equipped with an ABS system. This below<br />
standard performance however can be explained by a<br />
generally poor understanding of the system and a feeling<br />
of increased safety due to this systcm, which is generally<br />
badly used. This hypothesis is upheld by the intcrviews<br />
donc during the tests. In these interviews, thc subjects<br />
describcd thc ABS system as a device cnabling more<br />
effective and higher quality braking (i.e. optimal,<br />
stronger braking with braking distance greatly shortened<br />
undcr all circumstances).<br />
<strong>The</strong> difficulties experienced by thc subjects in spon'<br />
taneously activating the ABS system may be due to a<br />
high level of conditioning to normal breaking and the<br />
fear of locking the wheels. Thcse would suggest that the<br />
presence of an audible signal or a signal light indicating<br />
whether the ABS systcm has been activated or not would<br />
be helpful.<br />
s7.o.08<br />
Crash Avoidance Capability of 50<br />
Lennart Strandberg<br />
Swedish Road and Traffic Research Institute,<br />
VTI<br />
Abstract<br />
Experiments were carried out with more than 50 nonprofessional<br />
drivers making acceleration, dccclcration<br />
and lane change manoeuvres on ice at speeds where<br />
skidding was expccted. <strong>The</strong> subjects drove their own car<br />
and four reference cars (Volvo 440 or 740) with front or<br />
rear wheel drive, and with differently studded tyres. <strong>The</strong><br />
810<br />
It is of interest to note that a large number of subjects<br />
who could not avoid the obstacle considered the<br />
manoeuvre too difflicult, even impossible, to carry out.<br />
Thcsc subjccts cxprcssed surprise when they learned that<br />
others had succeeded in avoiding thc obslaclc. Professional<br />
test drivers who participated in the preparltion<br />
of this experiment rilted the milnocuvrc doablc but ditficult.<br />
This demonstrates the intcrcst in crrrying out<br />
further testing on safety systcms with non-professional<br />
drivers,<br />
<strong>The</strong> influence of age curently cannot be cortsidered its<br />
it can only be seen as a reflection of the importancc of<br />
the length of a person's driving experience (deterrnined<br />
by the length of time a per$on has had his/her driver's<br />
license). It is important to notc at this point, the poor<br />
performance of subjects who havc had less than 6 years<br />
driving experience.<br />
References<br />
Dittmar. A., Saumet. J.-L. and Vernct-Maury, E.;<br />
--Apports<br />
des paramdtres lhcrntovasculaires dans<br />
I'analyse de la rdponsc dlcctrodermale;" J. Physiol.,<br />
Paris, pages 80, 3, 22, 1985.<br />
Lechner. D.. Van Elslande, P. and Jourdan, J.-L.;<br />
"Utilisation<br />
d'un systEme ABS par des conducteurs<br />
non prof'cssionels lors d'un frcinagc cn courbel"<br />
INRETS report #4; 1989.<br />
Lechner, D., and Malaterre, G.; -'Expdrimentations<br />
de<br />
manoeuvres d'urgence sur simulateur de conduite;"<br />
Second part : "L'lrralysc ditailld des manoeuvres;"<br />
INRETS report #103; 1990.<br />
Malaterre, C. and Lechner, D.; "ExpCrimcntations<br />
de<br />
manocuvrcs d'urgence sur simulatcur de conduite;"<br />
First part: --comportement<br />
des conducteurs;" INRETS<br />
rcport #104; 1989.<br />
Thomas. C.. Koltchakian, S., TarriEbre, C., Tarribre, 8.,<br />
Got, C., and Patel. A.; "Les prioritds en sdcuritd<br />
primaire que disigncnt les limites de taisabilitd<br />
technique en sicuriti sccondaire automobile;" XXIII<br />
F.l.S.I.T.A. conl'erence: Mav 7-ll, 1990.<br />
Drivers in Different Cars on lce<br />
ABS-function was switched on or off. <strong>The</strong> reference cars<br />
wcrc tcstcd by the drivers in different order according to<br />
a Latin-Squarc dcsign. In a cotnbined braking and<br />
smooth lane change miln()euvre, AtsS incrcascd thc avcrage<br />
decelerirtion significantly. Stccriltrility and stability<br />
were also superior with ABS: lane marks hit in one (l)<br />
of 208 tests comptred to 30 of 208 tests without ABS.<br />
Dccclcration wa.s ZOVo greater with fully studded tyres<br />
than with basic studding on rll wheels. In a non-braking<br />
but more severe double lane change manocuvre, Loss-of-<br />
Control (LoC) occurred in 407o of thc tcsts with oversteering<br />
properties, induccd by front biasing stud
protrusion and number. If front and rear tyrcs were<br />
switched to understcering, less than 20Vo of thc tcsts<br />
resultcd in LoC. With all tyres fully studded, front<br />
driven cars had 309o LoC, which was 2-3 times grcatcr<br />
than for the larger rear driven cars. Still, the larger cars<br />
werc superior in manoeuvrc severity quantitics, such as<br />
lateral accelcration derived from spccd and path geometry.<br />
<strong>The</strong> corrclation of these quantitics to LoC relative<br />
frequency was not confirmed by the present study.<br />
Several observations give cause for morc emphasis on<br />
vehicle dynamics in driver education.<br />
Introduction<br />
Bat:kgrountl<br />
<strong>The</strong> safety potcntial of modern vehicle tcchnology<br />
may be lost, if drivers do not utilize the crash avoidancc<br />
propcrtics in emergencies. But also in normal driving on<br />
slippery roads, appropriate drivcr bchaviour v[ries considerably<br />
between cius. <strong>The</strong> nccd of drivcr education in<br />
safcty-rclevant cflr differences has bcen confirmed in<br />
personal communication with driving teachers and from<br />
vehicle dynamics oriented analyses of individual accidents.<br />
AIso accidcnt stittistics indicate thot considcrflble<br />
safety improvcmcnts may be achieved with morc emphasis<br />
on natural science knowledge in drivcr cducation and<br />
in vehicle maintcnance, see Strandberg (1989).<br />
It is true that the physical cfficicncy of crash<br />
avoidance cquipment such as anti-lock brakc systems<br />
(ABS) have been demonstrated by several investigators:<br />
e.g. Johnsson & Knutsson (1973); Rompe ct al (1987);<br />
Robinson & Riley (1989). But in recent yeius the effect<br />
on the real accident risk from ABS and other safety<br />
justified measurcs has becn questioned hy rcsearchers,<br />
see OECD (1990). Even if one does not accept thc Risk<br />
Homcostasis<br />
"theory" (Wildc, 1988) as a fruitful<br />
explanation of negative results, Bichl et al (1987) and<br />
Aschcnbrenner et al (1991) showed scicntifically that a<br />
group of taxi drivers drovc more risky when their car<br />
had ABS (compared to identical cars without ABS).<br />
Unfortunately, many non-scientists intcrprct such<br />
results as a proof of ABS usclcssness for safety. However,<br />
with minor educational efforts, ABS may contribule<br />
substantially to crash avoidance. Priez et al (1991) found<br />
encouraging improvcments in the avoidance manoeuvre<br />
performance of non-professional drivers with ABS cars<br />
after a half day's education. <strong>The</strong>ir experiments were<br />
carried out two months after the ABS-coursc. hcnce<br />
pointing at lasting effects. Many ABS car drivcrs without<br />
ABS-education did not grasp the opportunity to steer<br />
whilc braking, because they thought thlt ABS mrkcs lhe<br />
stopping distrnce much shorter. Thcrcby, they were less<br />
successful than thcir matches (also without educntion and<br />
in an ABS car) who wcre not aware of that the car had<br />
ABS.<br />
Though we did not intend to invcstigirtc the ABS<br />
training effects, the results and experiences from the<br />
present study indicate that propcr ABS behaviour may be<br />
Sectlon 3: Technlca, Sessions<br />
achieved with only a few minutes demonstration and<br />
driving practice. Unexpected result diffcrcnces in this<br />
investigation bctwcen tyres and hetwccn I'ront ilnd rcar<br />
wheel drivcn cilrs are other exanrplcs of the safety<br />
potential in bcttcr knowledgc on drivcr-vehicle interaction.<br />
Objettives<br />
<strong>The</strong> main and gcncral purpose of thc cxpcrimcnls<br />
reporlcd here was to increase our knowledge on how the<br />
avcrage driver copes with thc diffcrences on ice between<br />
cars and tyres, that ilre common on the roads and that<br />
may have contributed to serious skidding accidents. Data<br />
allow comparisons lrctween ABS and convcnlional<br />
brakes, betwccn four different mountings o[ two types of<br />
studded tyres, betwccn ltlcral. lorward, and rcrrward<br />
accclcralion (decelcratiorr) capubility, between dil'fcrent<br />
drivers (and belween Fronl and Rc;rr Whccl f)rivc. providcd<br />
thut olher diflerences bclwccrr thc actual FWD and<br />
RWD cars can be neutralizcd or ncglccted). Such conrparisons<br />
will bc prcsented in this paper.<br />
Sincc this knowlcdge will be (and has been) uscd in a<br />
developmcnt progrilmme for driver educltion and skid<br />
training (VTI, 1990), we hud to put realisrn (validity)<br />
and overview bclorc statistical power (reliability) on a<br />
few predctcrnrincd issucs. However, the rccordings lrom<br />
thc cxpcrimcnts constilute a data hlsc intcrrrlcd for pilot<br />
investigations of a number of other questions-rclcvant<br />
also in the developrnent of vchiclc lechnology and aulomotive<br />
$ystems that help thc driver ttl avoid accidents.<br />
One of the four test cirrs was cquippcd with ln onborrd<br />
computer and motion sensors l'or rccordings and lilter<br />
(not in this paper) evalualions wilhin thc European<br />
research prograrn rnc PROMETHEUS.<br />
Method<br />
'I'ime Ilislory and ()vervien,<br />
Thc cxpcrimcnls were carried out on a frozen lake<br />
(Hcnrsjon) in lhe county ol' l)irllrrra during the lhree<br />
winlcr vacalion wecks ol' | 990 (Swcdislr schools arc<br />
closcd onc wcck in Fcbruirr-y- March every ycur for<br />
winter sport activities). M0sl oI thc drivcr subjecls wcre<br />
tourists contilcled by invitation to :rddrcsscs supplicd by<br />
the tourist officc in the town of Orsa.<br />
A few days before colnmenccrncnt, thc ntild weather<br />
forced us lo tnovc lhc tcst statiOn 60 km away l'rom<br />
Orsa. <strong>The</strong> late move to a compflratively isolatcd spot<br />
made it virtually impossible to keep the test lrack in the<br />
same intcndcd conrlitiorr. Some planned nreilsurelnents<br />
and other activitics hld to be abrndoncd or sirttplificd on<br />
days when lhe wellher and failing cquipntcnt took all<br />
availablc rcsources. In addition, high temperature and<br />
melting ice causcd various praclical problems disturbing<br />
lhe experintcntal proccdurc. Thsrsforc. a sound scientific<br />
skepticisrn towards the rcsults is rcconrmcnded. Due to<br />
the practical problems our teilrn sonrctimes had to work<br />
l5-20 hours a dly. Though some fatigue mistakes have<br />
8ll<br />
ri<br />
*
lSth lntemetlonal Technlcal conference on Experlmental safety vehlcles<br />
been discovcred and compensated for, other problcms<br />
may imposc unknown bias. For instance, the pflrticipating<br />
suhjects drovc 120 km extra distancc in lheir own<br />
cars on slippcry winter roads during their vacation. Thcy<br />
arc probably represcntativc for a more skillcd driver<br />
population than the average on Swcdish roads.<br />
A test scssion took about 3 hours and involved 2<br />
subjects driving their own car in the first and last test<br />
runs. <strong>The</strong> tcsts with (and data on) lhc drivers' own cflrs<br />
arc not considered in dctail in this papcr. In the major<br />
part of a session, 2 front and 2 rear wheel drivcn Volvo<br />
"rcference<br />
cars" wcrc used with anti-lock brakes (ABS)<br />
in lunction or disconnccted by the instructor occupant.<br />
Winter (Mud+Snow) tyres with two dissimilar stud configurations<br />
wcrc mounted in pairs at the front and rcar<br />
axles to give the referencc cars neutral, undcr- or<br />
overstcerin g propert ies.<br />
Normally, two sessions were carricd out per weck-day.<br />
Due to unusually high tempcrature on February 20 and<br />
similar problems during the week-end between weeks<br />
no.tt&9. four sessions had to be callcd off. (We almost<br />
gave up after tcn scssions when the icc was covered with<br />
some hundred millimeters of water and broke up at the<br />
ordinary entrance palh.) I{ence, data from 26 sessions<br />
havc been collected. Thc wcather problems forccd us to<br />
usc up almost all grantcd resources in thc field experiments,<br />
leaving too little for a rcasonably quick and<br />
exhaustive evaluation. ln the projcct tearn we are thcrcfore<br />
interestcd to continue evaluation and analysis in<br />
cooperation wilh people outsidc thc Swedish Rord and<br />
Traffic Research Institute (VTI).<br />
Reference Cars<br />
<strong>The</strong> rcfcrcnce cars providcd by Volvo werc dcsignated<br />
A&B (front wheel driven Volvo 440GL), and C&D (rear<br />
wheel drivcn Volvo 744 GL). All of them wcrc 1990<br />
year modcl with manual S-spccd transmission and their<br />
maker's numher of chassis wcrc A: KX183ELC063932,<br />
B: KX183ELC064326. C: 744882L1400122. D: 744883-<br />
L1400227. Some of thcir tcchnical specificrrtions are<br />
given in Tablc l. Drivers' own cilrs wcre designatcd E<br />
and F, hut in computcr recorded datil itnd in rcsult tatrlcs<br />
both cars of thc drivers in a session have been labollcd<br />
E. <strong>The</strong> same Mazda 6264 Wheel-Stccring with unstuddcd<br />
M+S tyres (providcd for our 4WS practicc by the<br />
Swcdish Mazda importer) was lent to four car-less<br />
drivcrs as their "owtt" car in sessions no.Z. ltt, 19,22.<br />
Otherwise, all own cars ilre diffcrcnt. In this paper drta<br />
will not be presented on drivcrs' own cilrs tnd lhcy will<br />
bc disregarded in most o[ the test rcsult prcscntations.<br />
In all reference cars a video cilmeril wils moutrted<br />
behind thc front seats. In car D computerized meilsurcment<br />
equipmcnt occupied the front passenger scat. <strong>The</strong><br />
computcr and its operator-instructor were in the rcilr scat<br />
of car D, hence heing morc rcar hiased in wcight distribution<br />
than car C, which hrd no measuring equipntcnt.<br />
Thc instructor was scatcd in the front pflsscnger seat in<br />
812<br />
all othcr cars (A, B, C, E, F). An optional switch madc<br />
it possiblc to connect or disconnect thc ABS from tlrc<br />
fronl seat.<br />
Table 1. Manulacturer's (Volvo, 1989 & Hansson, 1gg1)<br />
Technical Specifications for Reference Gars Used in<br />
Experiments<br />
Drivm whels<br />
hcth (-)<br />
width (m)<br />
Whel-bM(E)<br />
Tmk frdthfiont (m)<br />
1 rrck width-rer (m)<br />
NoBisl kErb wcitht wilh 70kE drivcr (k8)<br />
Norninal wci8hi distrihution l:ront:RHr (fr)<br />
Msimum m8inc F ws (kW st Rev, tFf qond)<br />
NoEirsl fllio w$i8ht/Fower (k8fthl)<br />
Rsr m fmnt ntio of bntc lining hydnrulic pffiu$<br />
ABS brke ftoth hrve 3 qbruels, muMl rqr contrcl)<br />
WL<br />
Front<br />
4.31<br />
1.67<br />
2.50<br />
1.42<br />
1.43<br />
1100<br />
6l:39<br />
75 ar 93<br />
10.8<br />
RedEd at hiSh<br />
l'Gs<br />
Teve<br />
c&D<br />
744cL<br />
Rtr<br />
4.85<br />
1.75<br />
2.7't<br />
1.4'7<br />
1.46<br />
1370<br />
55:45 lD: rw hial<br />
85 at 90<br />
11 ,8<br />
Rsr sm ss fmil<br />
B{rsch<br />
Mcilsurcnrcrlls wcre rlso rccorded with a driver from<br />
the invcstigation learn in a Volvo 74-5<br />
"calibration" car<br />
cquippcd with urrstudtlcd M+S tyrcs of the satne lype<br />
(6islaved Frost) as on thc curs A-lJ. Scc scction hclow<br />
on Experimental Dcsigrr.<br />
Tyrrs<br />
Two studdirrg configurations wcrc uscd with the same<br />
type of tyre, see Figurc l&2. Thc Nivis Gislaved company<br />
provided 22 wlrccl.s with .,;tudded lyrc:s, lhat had<br />
been run-in at lclw speed on barc roads [o secure the<br />
studs in ths rubhcr for conslant stud protrusion during<br />
the cxpcrirncnts. Howevcr. rncusurelnents on l2 studs per<br />
tyrc tl'tcr thc cxperirnents rcvcaled substanlial dcvintions<br />
from thc rcquested prolrusion, see Ttble 2. (On Swctlish<br />
roilds, cilrs must nol hilvc ntorc than 150 studs pcr tyre<br />
and thc rnaximunr pcrnrissible protrusion is 1.5 nttn")<br />
Figure 1. Detail of a Basic Studded Tyre After the<br />
Experiments<br />
Figure 2. Detail of a Fully Studded Tyre After the<br />
Experiments
Table 2. Tyre $tudding: Protrusion es Intended Before the<br />
Erperiments, and Measursd on 12 Studs/Tyre Aflerwards<br />
Tyre Studdiru<br />
FWII: c#A&B<br />
RWD: csrC&D<br />
Bsicr Bsic:<br />
(70 c|utb/tyry) (t0 ctu&lryrc)<br />
FMI Whcl Drivc Rflrwhel Drive<br />
(1,10 studr/tyn) (lr|{} rludr/tyn)<br />
Prctuion bcforc Abdrt0.5ou About0.5tm About l.5DD Abqrt 1,5 ilm<br />
Frctruim rfrai<br />
lffiild ilhhlal<br />
69 fr (of 4[ sfrds) 2 t fr (of 46 shd$)<br />
1.0 m or mc 1.0 mm or mE<br />
s?fr (of t4 *rudr) A5 ft (of Ea rhda)<br />
2.o mm or mrc l.d mm or mrc<br />
M + $ Gislaved Frost Tyres made by Nivis about four monlhs<br />
before the experiments. Dimension 175/65Fl14 (Front Wheel<br />
Driven cars AaB) and 185/65R15 (HearWheel Driven cars C&D).<br />
Tyre tread pattern about 9 mm.<br />
Unfortunately, we were too short of resource$ to<br />
follow thc Nivis people recommendations to rnove the<br />
wheels bctwccn sessions from one position to anolher in<br />
the cars. <strong>The</strong>refore, thc protrusion varied also within the<br />
four groups in Table 2. Ncverthclcs$, thc dcviations are<br />
consistent with the observation that thc incrcasc in<br />
protrusion (occurring particularly whcn driving with<br />
great adhesion utilization on icc) is morc pronounced for<br />
FWD cars, Strandbcrg (1989). This will be discussed<br />
under a $eparate subhcad in the Double Lanc Change<br />
chapter below.<br />
Thc tyrcs were mounted differently on the cars lo give<br />
them pure handling propcrtics, see Table 3.<br />
Table 3. Denomination of the Four Studding<br />
Configurations Used on the Reference Cars A-D<br />
tvrc Studdim Conficumtion dr ar Ets Basic Mrri 6vm'*<br />
TyH d frcnt srle (notrtion in Trhlc 2)<br />
Tvru at lw $lo lnohtion id Tiht. ?l<br />
Bsic<br />
Full<br />
Brsic<br />
Brsic<br />
FUU<br />
Full<br />
Futl<br />
BNic<br />
Measuring Equipmrnt and Recordings, Personnel<br />
Three stationary speed sensors and thc stopping<br />
position reportetl by an observer beside the test track<br />
madc it possible to cillculale irverilge acccleration and<br />
dcceleration valucs on basis of thc pirth geomctry (the<br />
lateral accelcration cquation takcs thc car width into<br />
account, as wcll).<br />
One Speed Sensor (SS) consists of two infrared light<br />
emitters and two detectors. <strong>The</strong>se cornponcnts wcrc put<br />
ilt a reasonahly safe distance from the path and lhc lrnemarks,<br />
the emittcrs to thc lcft and thc dclcctors to the<br />
right. <strong>The</strong> dislance bctwccn lhc two cntiilr.:r-dclcclor<br />
pairs was S m for SS no. I and I m for SS2 and SS3.<br />
<strong>The</strong> time between light trcam disluptions was dctermined<br />
with a computer also calculating the speed (average<br />
bctwccn thc cmitter-detector pairs) and presenting lhe<br />
value at a display in the testing base. <strong>The</strong> conrputer has<br />
bcen developed at VTI for use with cahlcs irnd otlrcr<br />
types of vehicle detectors in a systcm called PTA<br />
(Portablc Traffic Analyzcr) for determinttion of speed.<br />
lateral position, vehicle type, etc.<br />
<strong>The</strong> tests were governed from the testing base (a<br />
warmed-up Van-type car) by the test manager. <strong>The</strong> base<br />
was put behind snow banks about lOrn to the right of the<br />
first lane-marks in thc tcst track. A vidco camcril outside<br />
the base was recording the tests hut frequent drop outs<br />
Sectlon 3: Teehnlcal Sesslons<br />
occurred due to wind. snow tnd electro-milgnetic noise<br />
from thc PTA computcrs close to the video recorder.<br />
In all rel-erence cilrs a vidco ctrngril was nrounted<br />
bchind thc front sclts, ror'mllly recording a whole<br />
session including sound frorn the radio comrnunication.<br />
Thc pictures may tre used for qualitative inforrnation on<br />
car and stccring whccl motions. During pauscs bctwccn<br />
the tcst runs, thc instructors filled in a qucstionnaire on<br />
thc drivcrs pcrsonal dltu, annual milcage and experience<br />
from different car types, from wintcr-timc driving and<br />
from accidents. <strong>The</strong> sarne lbrm and thc sarne inslructor<br />
followcd thc driver wlrcn changing bctwcen cars. This<br />
"driver<br />
lorrn" was glso uscd for tcsl oulcoriles and data<br />
such as notes on skidding, clulclr dcprcssing, subjcctive<br />
judgements on steering corrcctions (uscd to distinguish<br />
belween 0 and I in the Loss-of-Control Scorc. see<br />
section on Loss-of-Control slalistics lrclow). dernanded<br />
speed and speedomeler relding (l'or dctcrnrining r suitable<br />
speed chlngc l'or lhc ncxt Doublc Llnc Changc<br />
manoeuvre in radio discussions bclwccn thc inslructor<br />
and the test nranlgcr).<br />
Thc mcasuring computer in car D recordcd thc litne<br />
histories of thronlc position, steering wheel angle,<br />
longitudinal and latcral accclcralion, longitudinal<br />
velocity, yaw vclocity, in addition to cvents such as<br />
deprcssing the brakc or clutch pcdtl. <strong>The</strong> 8 channels<br />
were sanrpled with 20 Herz during 40 scconds pcr tcst.<br />
Such records frorn sevcral hundrcd tcsts arc avaihhlc on<br />
PC-media for further analysis. Succcssl'ul attcrnpts have<br />
bcen madc to cornpule non-recordcd viu'iables such as<br />
yaw lnd sidcslip anglcs. Thcsc data may irnprovc our<br />
knowledge on how dill'crent drivcrs pcrccivc and ncgoriate<br />
skiclding molions. Ihough they are not elahorate d on<br />
in this paper. Hitherto. dittil huve been processed with<br />
Exccl in MS-Windows and trc storcd on IBM compatible<br />
PC-nredia.<br />
Since importrnt prrts of thc cxpcrimcnts wcrc unrehearscd<br />
and required a greilt dcal of practical expericnce<br />
from lrolh driving and teaching other drivers as wcll as<br />
of exlempurary cnginccrirrg, the pre scrrtalion would nol<br />
be cornplcte without a l'cw words on thc pcrsonll background<br />
of lhe tcsl lcurn rclcvanl lo lhcir rolcs on silc.<br />
(Of coursc. olhcr pcoplc hlve contritrutcd substantitlly<br />
to llrc invcstigltiorr during prcpitratiolt and cvalualion.<br />
But this dcscription conccntriltcs on thc tcst site<br />
activilics.) Narncs in alphrbcticrl ordcr.<br />
Stcfln Bcrglund (instructor irnd computer operator in<br />
car D) has praclical expcricnce fronr nrcchanical und<br />
clsclronical cnginccring ut VTI lnd privatcly with<br />
various cars. Now also racing a Bo cart of his own.<br />
Svcn-Akc Lindrin (tcst milnlgcr and responsible for<br />
selcction, prcparation and opcrltion ol' thc le.sl s^ile as<br />
wcll as for lodging and socitl flrrangcrncnls) hls decldes<br />
of similar experience from VTl. He is also considcrcd<br />
(one of) the institute's most reliable test drivers. Now<br />
teacher at the Volvr-r Dvnitmic Sal'ctv Drivins School.<br />
8l<br />
:':.<br />
lt<br />
,.<br />
r<br />
;<br />
-;i<br />
,
,<br />
lflth lntematlonal Technlcal Conterence on Experlmental Safety Vehlcles<br />
Lennart Strandberg (project manager, responsible for<br />
experimental design and for safety-rclcvant manocuvres)<br />
has experience from driving rallies and Swedish ice<br />
racing championships, from accident analyses and driving<br />
school cooperation on skid-pad training, and from<br />
scientific testing of technical properties with human<br />
subjects.<br />
Harry Sdrensen (instructor and operator in car D also<br />
responsihle for its computer programming and its<br />
measuring equipment) has a long time expcricnce from<br />
VTI on design and managemcnt of measuring equipment<br />
for tcsting of car handling properties.<br />
Jerry Wallh (car testing manager and "calibration"<br />
driver, responsible for transports and communications at<br />
the test site) has several ycars professional experience as<br />
an ambulance driver in the fire brigade. Now responsible<br />
for the test vehicle fleet and vchicle techniques laboratory<br />
at VTI.<br />
<strong>The</strong> Swedish Federation of Women's Motor Transport<br />
Corys (SKBR) contributed most of the time four workers<br />
in different roles.<br />
Kicki Hellstrdm chairperson for thc Dalarna county<br />
branch of SKBR found extremely capable larlies working<br />
one week at a time as insttuctors, track managcrs and<br />
observers, lane-mark positioners, duty vehiclc drivcrs,<br />
video operators, photographers, ice drillers, srlow<br />
removers, receptionists, ctc. <strong>The</strong>y fulfilled their tasks<br />
under primitive conditions after a few hours traiping on<br />
Sunday afternoon befoie their week on duty. In spite of<br />
our poor knowledge at that time on the frequent ABSconfuses<br />
among non-professional drivers, the results<br />
from the (Combi) braking tests show that the instructors<br />
in a few minutes succeeded to teach the drivers how to<br />
improve their deceleration capacity with ABS. <strong>The</strong>ir<br />
name$ are Berith Andersson, Eva Biicksholm, Inga-Lill<br />
Camitz, Rita Eriksson, Sylvia Krcnn, Christina Lckman,<br />
lng-Marie Persson, Kerstin Sunnerby.<br />
Driver Subjects<br />
Thanks to cottage rental agencies we could mail<br />
invitations to about 300 tourists, intcnding to spend their<br />
winter sport vacation close to thc town of Orsa. <strong>The</strong><br />
number of people who acceptcd to participats was more<br />
than sufficient as long as we stuck to our plans to test on<br />
the Orsa Lake. However, the high tempcraturc in Orsa<br />
the weeks before the expcrimcnts forced us to move the<br />
test site about 60 km as mentioned above. Of course, a<br />
' number of subjects then withdrew from participation, but<br />
the mild weather made also skiing difficult.<br />
<strong>The</strong>refore, we could find driver subjects to all<br />
sessions, particularly after asking the local inhabitants<br />
around lake Hemsjon, where the tests finally were<br />
carried out. Six of the SKBR women and Stefan<br />
Berglund from VTI have also participated as subjects in<br />
sessions when the drivers on schedule did not appear.<br />
Howcver, no person has participated twice and all 52<br />
subjects are different individuals. Many of the partici-<br />
- 814<br />
b--<br />
pating tourists accepted to drive 120 km extra distance<br />
in their own cars on slippery winter roads during their<br />
vacation. Hence, our driver sample is biased and probably<br />
rcprcscntativc for a more skilled driver population<br />
than the average on Swedish roads. Drivers' sex and year<br />
of birth are given in Table 4, but other compillrtions<br />
from the questionnaire in the "driver form" will not be<br />
presented in this paper.<br />
Combi Manoeuvre : Accelerating, Braking, Steering,<br />
Stopping<br />
Thc combination (Combi) manoeuvre was designed to<br />
challenge the driver-vehicle ability to kccp cotltrol in<br />
acceleration, decelcration, and steering while braking.<br />
<strong>The</strong> driver was askcd to accelerate as lnuch as possible<br />
from standstill about 200 m bcfore the first lane-marks<br />
at X=0 in Figure 3. Aftcr having continued the acceleration<br />
for 80 metcrs in the left lane, the driver should<br />
makc a quick changc to trtaximutn deceleration bringing<br />
the car to a full stop without hitting the lane-marks.<br />
o<br />
o<br />
"s<br />
o<br />
o<br />
o<br />
o<br />
o<br />
o<br />
o<br />
o<br />
o<br />
o 3.im A<br />
oH<br />
+3.5 m<br />
:"*'"<br />
o 80o E<br />
o AGc I ".ry*.$ zooI<br />
o<br />
o<br />
\t<br />
J\<br />
-"2m6 (n) DLC<br />
olg0oEi<br />
H'lflt"J<br />
lE"170o<br />
,"1600<br />
o1500<br />
ol4{lo<br />
o1300<br />
o 90o<br />
o 600<br />
o 50o-------#r'ffi<br />
o {}o V<br />
o JQo<br />
.8.<br />
8"<br />
lf Marks at filled circles were removed when changing between<br />
o<br />
o<br />
.}ffi'*'<br />
o<br />
. $$t-r"* -oo<br />
o<br />
fio<br />
o<br />
10o o iiii,,., o<br />
ssr @wo<br />
o<br />
o<br />
,/rih<br />
o2j<br />
mo<br />
o{fi<br />
"mo<br />
o<br />
tlo<br />
, t b<br />
ffi ilo<br />
Ji i,a o<br />
o<br />
a o<br />
r 35m o<br />
a o<br />
"ffio<br />
manoeuvre gpes. SS1, SS2, SSg indicate the X-coordinates ol<br />
the infrared light Speed Sensors (put some meters bs$ide the te$t<br />
path to avoid damage upon loss-of-control).<br />
Figure 3. Path Layout and Lane-Mark Positions in<br />
Combi and in Double Lane Ghange Tests<br />
o<br />
o<br />
o
In most of the tests the car did not stop bcforc X=160<br />
m. Thcrefore, it was necessary to turn right during the<br />
dcceleration. However, the lane change could easily be<br />
made without need of skid provoking steering, provided<br />
the brakes were properly used. When the car had<br />
stoppcd, an observer reported its front end position by<br />
radio to the test manager, who wrotc it down in his<br />
"session<br />
form" together with the readings from the three<br />
Speed Sensors (SSl, SS2, SS3 in Figure 3). <strong>The</strong> car<br />
position was determined with an accuracy of about * I<br />
m by looking at the nearby lane-marks put in holes in<br />
the ice l0 meters from each other. Howcvcr, in 60 (of<br />
520) Combi tcsts the cflr stopped after X=20-5 m. <strong>The</strong>n<br />
it was morc difficult to assess the position, since only<br />
two lane-marks were present altcr the ones at X=200 m.<br />
If some lane-marks were hit, it was reported to the<br />
$ession form by the observer.<br />
In sessions when we judged the ice parricularly<br />
slippcry, the starting point was moved from l50m to<br />
200m before the first lanc-marks in the test track<br />
(distance to SSI designated So,). A too short accelerarion<br />
distance would give too low spccds in the path and make<br />
it too easy to stop bcfore X=160m without need of<br />
stecring into the right lane. In Table 4 thc comparatively<br />
small decclcrations at sessions with Sn,=2Q0m indicate<br />
that the subjective judgcments of slipperiness wcrc not<br />
too bad.<br />
Most of the lane-marks and the exit in the right lrnc<br />
were the same for both Manoeuvre types. Howcver, the<br />
exchanges between Combi and Double Lane Change<br />
arrangements were comparatively time-consuming and<br />
their number were therefore minimized in thc scssion<br />
agcnda.<br />
Doubte Lane Change Manoeuvre<br />
<strong>The</strong> Double Lane Change (DLC) test track gcomctry<br />
had been adjusted to imposc problems wirh srilbiliry and<br />
(rear wheel) skid control when the tyres wcrc similar at<br />
both front and rear wheels (Basic or Maxi Studding). In<br />
the pretests with Oversteering tyrcs, wc found lhe same<br />
geomeFy to be even morc skid provoking. Understeering<br />
tyres, on thc othcr hand, made the tests comparatively<br />
insensitive to the skills of the driver. When the<br />
demandcd specd was too greilt, loss-of-steering and<br />
"plow<br />
out" occurred often before completion ol'the first<br />
lane change to the left, which resulted in hitting of the<br />
lane-marks C70 & C80, see Figure 3. <strong>The</strong>refore, few<br />
tests were schedulcd with Undcrsteering tyres in the<br />
main program.<br />
In the ordinary DLC test, drivers were asked to kccp<br />
constant a ccrtain speed and to avoid hitting lane marking<br />
tubes. Since the ohstacle marks blocking the right<br />
lane (C70&C80 in Figure 3), determined thc latcral<br />
motion and the severity of thc manoeuvre, we had to<br />
exclude (disapprove) a test from analysis, if both these<br />
lane-marks were overrun, see Eq. 7. (In sessions no. ?l-<br />
Section 3: Technlcal Sesslons<br />
22 inflatatrle car dummies helped the drivers to irvoid<br />
such disapproval).<br />
<strong>The</strong> speed was demanded on radio by the test manager<br />
to provoke skidding-and loss-of-control in ccrtilin tosts<br />
with unskilled drivers. <strong>The</strong> instructor and test ntanager<br />
judged the driver proficiency during the initial training<br />
runs and in about four recorded DLC tcsts with the<br />
drivers' own car. In these first DLC tosts, the driver<br />
increased the speed in small steps. Ilowevcr, thc<br />
succeeding ordinary tests with the rcfercncc cars were<br />
only two pcr drivcr car combination and in some cases<br />
were both runs on the sarnc sidc of thc limit for loss-of-,<br />
control. To minimiz.e thc nurrrber of driver-cars with such<br />
unspecilic results, the speed was dernanded as follows.<br />
If the driver had no problcm in rhc firsr DLC with a<br />
reference car, the test rnanagcr rcqucstcd a specified<br />
increase (5 or lOknr/h) of thc specd in the second tcst<br />
and vice versa. Only if thc first run exhihited pronounced<br />
skidding wilh recovery and il' lanc-rnarks wcre<br />
hit in thc first run, thc sirmc speed was demanded in the<br />
second DLC tcst.<br />
Experinzentttl Design<br />
To neutralize driver learning and fatigue efflccts on the<br />
differences between refercncc cars and hctwccn tyre configurrtions,<br />
they were tested by the drivers in diffcrcnt<br />
ordcr. In scssions l-8 & 9-16 respectively, every rel'erence<br />
car wils presentcd to four drivers in each sequcntial<br />
position (lst, 2nel, 3rd,4th), and in session l7-18 to one<br />
drivcr in eflch posilion. Tyre configumti()ns remained unchanged<br />
within these groups of sessions, scc Tablc 4.<br />
Sessions no. 14. l7 and no. 19-26 includcd so ctllcd<br />
pedal tests (Double Lane Change with clutch, throttle or<br />
ABS-brake activation). <strong>The</strong>y wcre carricd out only with<br />
the computerized Rear Wheel Driven car D and with one<br />
of thc Front Wheel Driven cars (A or B). To avoid<br />
learning or confusing effects on the ordinary DLC<br />
manoeuvres, all pedal tcsts were schedulcd to bc thc<br />
driver's last t)LCs wilh lhe two cars in qucstion. Duc to<br />
excessive tinrc consurnption for thc additionill pcdal tcsls<br />
in scssions 14 & 17, thc ordinury progrilm had to be<br />
rcduccd to allow tor pcdirl tesls in the last eight sessions<br />
(no. 19-26). It was decidcd to abandon thc DLC rcsts<br />
with car C, bccausc thc wcight distribution and handling<br />
propcrtics wcrc considercd more clifferent between car<br />
C&D than bctwccn clrr A&8. Since we intend to present<br />
the results of pedal tcsts clscwhcrc, they arc normully<br />
disregarded in this paper.<br />
When excluding car C from the DlC-tests in sessions<br />
l9-26 wc also dccidcd lo rlount Understeering tyres on<br />
it. <strong>The</strong> Combi tests would thcn bc complctc with all carstudding<br />
combinations. And in the DlC-manoeuvre we<br />
expcctcd that many tcsts had to be withheld from analysis,<br />
since both marks blocking the right lane (C70 & C80<br />
in Figure 3) often wcrc hit in the pretesrs with<br />
undcrsteering.<br />
815
13th lnternatlonal Technlcal Conference on Experlmentel Selety Vehlctes<br />
Since car C wils not used at all in the DLC<br />
manocuvrc, only two (anti-symmctrical) car pcrmutations<br />
were scheduled in sessions l9-26. Comparisons of DLC<br />
rcsults from thcse scssions should therefore be made<br />
with caution-and preferably between car A and B<br />
(Front Wheel Driven). However, comparisons between<br />
cars C and D seem justified in Combi tests.<br />
Table 4. Experlmental Condition$ in Ordinary Sessions<br />
I<br />
6<br />
1<br />
9<br />
l2<br />
l5<br />
t0<br />
?l<br />
27<br />
25<br />
26<br />
cnilFIcG c4[ro8r!m + Mdil'oHr Fdir l.ilrwilh r'il Aau<br />
wis c.iC onlv Coditrilrs.E ild.d wt (ru plc{t'rHvftr i. ^dditionll p.d!l l.ilr *ilh {rB BD<br />
htrklbl..!r dud.r (Dintusiry 'k vilql in!'ttinil.f ordiMs philii tub{ lintsrr},) Pur wrEd Irft.bS<br />
S01 =acceleration distance lroifl start to "entrance<br />
gete' (f irst lanemarks).<br />
<strong>The</strong> Driver 1&2 d-.. (Eq.4) deceleration results (mean<br />
values over car A-D) indicate the variation between sessions in<br />
ice friction.<br />
Two Combi tests were carried out with each pair of<br />
car and driver. <strong>The</strong>refore, learning and fatigue cffccts on<br />
comparisons bctwccn ABS and Standard (STD) brakes<br />
wcrc ncutralizcd by reversing the testing order for the<br />
two drivers in each session. When Driver no. I begtn<br />
with ABS, Driver no.2 had Stlndard brakes in the first<br />
Combi test with all cars A-D. To minimize the variancc<br />
from the successive within-session chtnges in icc roughness<br />
(due to the studded tyres and bccausc of wcathcr),<br />
ABS and STD tests were made directly after each other.<br />
Only one tcst run by thc othcr drivcr camc in bctwccn.<br />
Evcn if thc changes in ice roughncss and friction may<br />
be ncutralizcd within the sessions, considerahle variations<br />
have been observed between sessions. See the last<br />
columns in Table 4 and Figure 4. Separate tests were<br />
carried out with a driver from the investigation team in<br />
the "calibration" car with unstudded tyres of the same<br />
type as on the cars A-D. However, tirne constrilints- and<br />
practical problems limited the possibilities to run calibration<br />
tests frequently enough. Snowfall and wcathcr<br />
changes in many sessions introduced substantial friction<br />
variations with time and with driver path selection. In<br />
addition, the corresponding variation in the relationship<br />
between studded and unstudded tyres is so poorly known<br />
that we have not yet tirund any satisfactory method to<br />
utilize these calibration data.<br />
816<br />
s0l<br />
Tyr tlE TyE TyE h".rF.l D;v.rt.<br />
sild ltud stud srud &D,2, sq. nd.l<br />
d,d8 diry diq diry nrbBl.<br />
Clr C.r C.r Crr 3.q".,t'rt dd.r .onfi8. in<br />
^ a C D dfftftEd.orE Cohbik'<br />
^. s. c.D<br />
150 Mnx ftr Mrr (F.<br />
150 Mrr or, M.x (tr<br />
lt0<br />
Mrx tur<br />
-E;<br />
Mlx fir<br />
lt0 M,-<br />
ffi<br />
150 Mlx &r &r M.r<br />
lJ0 Mrx ar h. Mlx<br />
2m<br />
tm<br />
150 Mix &r MrI Er<br />
t5a<br />
lJ0<br />
t50<br />
lJ0<br />
150<br />
lJ0<br />
154<br />
m<br />
Mrr tFr Mlx fir<br />
Mrx 6r Mlx ftr<br />
Mlx ftr Mu Sr<br />
Mrr (*, Mrx tur<br />
Mrr k. &r Mlx<br />
ht Fr tu ilrx<br />
Mlr h! hr M'"<br />
M.r kr &r Mlr<br />
Mix hr hr M'r<br />
Mdx hr Mrr tu"<br />
Urd ftt Ad O"r<br />
tril 6. Ud fir<br />
Ud ftr Ud ()vr<br />
UilJ frr Ud &r<br />
Und ftr Ud rlr<br />
Und Fr !d (F.<br />
Vd h. Ud tu.<br />
ud frr Ud ftr<br />
L:BDAC ?:FBA ^F nn<br />
.51<br />
.sbAc!.c^DB s0,s<br />
LIMD1IEBA TTD'S F,1943<br />
L.BD^C 2.mDA s.sD<br />
LfADF?r^ED flrr^br M, l97l .1t<br />
L.^rcD 2 mBA fiL rEr<br />
.39<br />
lf&B l;FnAc ^E srD F,1970 .n<br />
l:MD z:FBA m ^N<br />
lrCMFlrBllac ^rt t'u M,1968 .lB<br />
I.BDAC!.rAA ^f,r.frn<br />
I:CADB Z AEfl} Til'. AtrX<br />
.5?<br />
I BD^C t.C&A s!,^Rr<br />
.J3<br />
.AH'D1mA^ rrDj^!r M, 1ff9 4t<br />
L.ADAC ?.CApB ^Er flD<br />
.17<br />
L AscD1.4.s^ ^Bjrt! M, lgt? ?!<br />
L ARCD 1 r-s^ ^Hrj ''D F, 196l ,t7<br />
F, l9S<br />
M,l94l<br />
ArcD z.FBA<br />
.91<br />
.98<br />
M,1945<br />
M, t9t8 .89<br />
.62<br />
m.rE<br />
A4b !.Eg^ ^4,s0<br />
ArcD 2:mEA m. ^s<br />
Amrr l rrg^ dri,ru<br />
^S('D I:EAA frqs<br />
atcD r,sisA ru rn,<br />
ABCD ? mRA 5r' ^trr<br />
l94l<br />
1939<br />
1947<br />
1945<br />
It4i<br />
t947<br />
l9?l<br />
l96J<br />
l9tl<br />
191?<br />
.0t<br />
.{3<br />
.Jl<br />
.Jl<br />
.5r<br />
,E<br />
:.15<br />
.5{<br />
r,3t<br />
.{l<br />
.72<br />
1t<br />
.6t<br />
.95<br />
1967 ,9J<br />
.81 ID<br />
1950 t.0t n)<br />
a)<br />
l9?0 .tt H)<br />
l5)<br />
Consequently, the evaluation .should bc ba.scd on<br />
variables as insensitive as possible to friction<br />
fluctuations. Somc attcmllts will bc prcscnted beklw, hut<br />
skepticism is recornmended and the author will gratefully<br />
receive constructive criticism and ideas for future<br />
research.<br />
Since the pretests were impeded by the move between<br />
the lakes of Orsa and Hemsjrin (68 + 97 + l4'l + 130 =<br />
442) additional tcsts wcrc madc altcr scssion no. 26<br />
during four days (March 3-fr). Only thrcc drivcrs (S-A<br />
Linddn, L Strandberg, J Wallh) from VTI werc involvecl-to<br />
reduce the vuriance in the handling property<br />
asscssmcnts for thc rcfcrcncc cirrr,^ flnd tyrc studding<br />
configurations in Table l&3. <strong>The</strong> calibration car was<br />
also uscd in thcsc tcsls to facilitate analyscs which may<br />
increrse our knclwledge on the questions menti()ned<br />
above. A considerable number of computer recorded car<br />
D motions are included in these data, which are lreing<br />
evalualcd in proporlion to availal)le resources.<br />
Results and Discussion: Combined<br />
Manoeuvre<br />
A.tlrg-rlrDrc.nt of D e te le ration and Forwartl At:ce leratitttt<br />
Two dcccleration valucs (d, and dr) has becn asscsscd<br />
for cach Combincd Manocuvrc (Combi) Tcst. Datr on<br />
the stopping distrrnce (S? & S3) lrom lhe Speed Sensors<br />
no. 2 & 3 (SSr & SS. in Figure 3) and on lhe corresponding<br />
speeds (v;) were used logether with the simple<br />
expression in Eq.l, where subscript i denotes the actual<br />
spced scnsor (no. 2 or no. 3).<br />
d.=<br />
Since the drivers were instructed to accelerflte up to S52,<br />
the brakes were not alwitys fully applied during the<br />
initial pilrt o[ tlrc S2-distance. Thcrefore, dr>d, in the<br />
avcrflgc Comhi lcsl, and d, miry hc considcrcd a morc<br />
precisc mcasurc oi the stopping capability than dr. On<br />
thc othcr hirnd, rrtissirtg dalir is more frcqucnt from SS3,<br />
sincc wc had lo givc priority to SS2 (ncccssary for<br />
cvalurtion of ttrc Doublc Lane Chtngc Mtnoeuvre) when<br />
snow and other factors caused drop-outs of thc scnsors.<br />
<strong>The</strong> accelerations ar (frorn stflrt to Spccd Scnsor SSI)<br />
and a,, (from SSI to SS2) were deterrnined similarly<br />
from the SSI and SS2 speed records, v, and from the<br />
ssnsor positions.<br />
2<br />
vl<br />
a,=- ,<br />
ZSu,<br />
etz =<br />
yr2 -v,t<br />
=o<br />
(2)<br />
<strong>The</strong> distance Sr2 between SSI and S52 was 70.-5 rn in all<br />
sessions, while 56, was either 153 m or 203 rn sincc the<br />
starting point somclinrc,s (when lhc ice was particularly<br />
slippery) was movcd lrorn l50m to 200m bcfore the first<br />
lane marks in the test track. scc Tablc 4 and Ficure 3.<br />
v<br />
' l s<br />
(l)<br />
(3)
Table 5 displays statistics on these quantities<br />
exprcssed as the "macro" (subscript mac) values of<br />
acceleration and deceleration. A few of the recorded<br />
sensor speeds Bflve unreasonably great deceleration<br />
values, probably bccause flying lane marks triggered the<br />
speed sensors. <strong>The</strong>refore, the next greatest value for each<br />
drivcr-car pair was selected by the computer program ss<br />
a maximum of thc medians of all (up to tour) dccclcration<br />
or accelcration triples according to the formulas:<br />
d =<br />
*" M AX(M e d i a t{douod*u.n/or"r),<br />
Mediarldrr or,,dr,rro,,4,r-),<br />
Median- -.)<br />
(4)<br />
d =<br />
*" M AX(M e d i a r(a y*sfl w r ao,o,,rro,),<br />
Mediar{aro^r.D,cr(sr'},ar:(s.rD}), (5)<br />
Median...)<br />
where the decelerations d, and d, are given by Eq. I and<br />
accelerations irr, arr by Eq. 2 &. 3. Thc rcsult sensitivity<br />
to variations in ice friction and in driver deceleration<br />
pcrformance are illustrated in Figure 4. Substantial<br />
differenccs arc exhibited between sessions, but also<br />
hctween drivers in certain sessions. Within a session it<br />
was not cxpected to find driver difi'crcnccs of such a<br />
magnitude, since each value is an flverrge of the "best"<br />
tests with the same four reference cars.<br />
:<br />
3.00<br />
2.50<br />
fra-D - ^^<br />
r+offhr l.w<br />
Dedmtion , .^<br />
(m/rl)<br />
Drlr*2<br />
l-s<br />
0,50<br />
J...<br />
-i<br />
i-'#<br />
r-r--!J<br />
o.oo]-<br />
0.00 o.50 t.00 1.60 2.00 2.50 3.OO<br />
CF A-D'mrmff' HFrai.E (E,/sl) Drivs I<br />
(in m/s'as the *macmean'deceleration<br />
(driver's avgragg ovar<br />
car A-D of the *macro'deceleration<br />
value: d-.o in Table 4 & Eq.4).<br />
Line y=1 overlayed. Linear regression forced through origin<br />
(y=mx) yields slope m= 1.01 and f=O.lZl<br />
Figure 4. Relatlonehip Betwssn the Two Drivers in<br />
Each Seselon Regarding <strong>The</strong>ir Deceleration Capabitity<br />
Dereleration and Controllability With and Withour ABS<br />
When evaluating the influcncc from ABS on the<br />
dcceleration capability, the (di) deceleration villucs were<br />
paircd for thc same driver and car. Since the Combi tests<br />
with and without ABS were made con$ccutively for<br />
every car driver combination, such pairing nrakes the<br />
results less sensitive to the tirnc varilrion of friction. and<br />
to differences betwecn drivcr.s, tyrcs, cilrs, etc. <strong>The</strong>refore,<br />
an ABS decelcration cnhancement Ratio (Ro,on.)<br />
was calculated (one for cach dr- or dr-deceleration value)<br />
accorcling to Eq.6:<br />
d,(n<br />
frr, ,<br />
r,<br />
=<br />
durr^<br />
l-tt<br />
J-<br />
'<br />
(6)<br />
Sectlon 3: Technlcal Sessions<br />
whcre subscript; metns the speed sensor numbcr (2 or<br />
3), subscript (ABS) dcnotcs a tcst run wirh ABS. while<br />
subscript (STD) is used for the corresponding tcst run<br />
(same car and driver) with standard or convcntional<br />
brakes, i.e., when the Anti-Lock funclion was disconnected.<br />
Table 5 exhibits statistics on thcsc Ratios for rhe<br />
four tyre studding configurations dcfined in Table 3.<br />
Tsble 5. Number of Driver-Stud Combinations with<br />
Complets Date (n), Corresponding Average (Mean) and<br />
Standard Error<br />
rtE<br />
hdft<br />
tu-a<br />
&B<br />
U SAH !dIAH n R{rrss RileH<br />
Md! Hd..r.<br />
n L r r l * n h r h<br />
20 1.059 0,0td 18 1,t25 0.0JE 2D D.U3 0.Sl ?o t.76t o.il6<br />
32 l. t66 0.037 t3 1.269 0.108 29 1.021 0.0J4 32 2.lT 0.056<br />
15 l.lo2 0.014 il l.t# o.M3 l3 0,999 0,053 16 r.790 0,067<br />
33 1.07t 0.025 l0 1.098 0.059 36 0.985 0.036 36 2.181 0.064<br />
lm l-roa 0,01t F LIS 0.m s o.ffi 0-01: lg .ora 0-H<br />
Rcfcrm<br />
n tutrc autss n rdffi xdaEs n r--<br />
l9<br />
il<br />
r6<br />
r4<br />
07E 0.055<br />
l4E 0.M8<br />
r6E 0-063<br />
130 0.02,1<br />
n rurm trm n<br />
Rolgs f,ctlns n t * t n n d-- Lr<br />
Md! tu-F-<br />
39 t.06E 0.012 34 1.090 0.01d { 0.796 0-uE {0 1,735 0.0t2<br />
62 1.15? 0.010 4r l.?17 0,{16l 58 0.913 0.029 64 ?.0?0 0.041<br />
J r t. 136 0.0t6 z?. Ln1 0.045 In n.915 0.037 32 1,888 0.048<br />
67 l.lo4 d-or? 5t l t04 0,038 72 0.936 0.025 7? 2.149 0,0,16<br />
lr l.ilt 0.01a lr7 r,ld 0.u! ls o.ffi 0-017 rB l,H 0,0rt<br />
l0 Lt16 o.tut<br />
16 1,051 0,t141<br />
20 1,158 0.055<br />
il l,?07 0.080<br />
?t Lllo 0.049<br />
20 0-749 0.074<br />
20 0,8tr o.o38<br />
13 0.9J1 o.o53<br />
hs n t u * L -<br />
1.703 0,llr<br />
1.915 0,054<br />
t.9t? 0.06?<br />
2. t 17 0.ffi1<br />
(Sld.err, = Std.d€v.Mn) of ABS deceleration enhancem€nt (HdiAEs,<br />
Eq. 6) as well as the 'macro" values of acceleration (a.." Eq, 5)<br />
and deceleration (d..", Eq. 4) given in m/sz.<br />
If thc means ale assumed to be t-distributed, the standard<br />
crror may be considered greater than a l/4 confidence<br />
intcrval (lcvcl 95% rt n>60, 9070 if n>6) for the<br />
mean. See e.g. Fishcr (l9.5tt) or Draper & Smith (1981).<br />
Hcncc, thc dccclcration cnhancement with ABS rnay be<br />
considcrcd stiltisticitlly significlnt.<br />
Under these conditions. thc averrge drivcr succccdcd<br />
to increase the decelcration with about l07o (lowcr Iinrit<br />
of lhe 95%-confiderrcc intcrval: 1.09
1lth tntematlonel Technlcal Conference on Experlmental Safety Vehlcles<br />
improvc their deceleration capability by locking the<br />
wheels and ignoring the lane-keeping task (which has<br />
been suggested in car- and tyre test rcports in some<br />
newspapers). This cvaluation of driver ctlntrol points at<br />
an ABS advantage, which may be even more irnportant<br />
to safcty than the deceleration enhancement.<br />
Deceleratlon With Different Tyre Configurations,<br />
Examples of Bias<br />
<strong>The</strong> advantage of having wcll-studded tyres on the<br />
driven whccls is reflected by thc Sreater acceleration<br />
(a-"") mean values in Tablc -5a (Oversteer row) and in<br />
Table 5b (Understeer and Max studding rows).<br />
Considering the Front Driven cars in Table 5a, the<br />
comparatively great acceleration capability of the<br />
Understeered configuration may reflect a bias due to<br />
greater friction on the acceleration path during the last<br />
cight sessions (no. l9-26), which were thc only ones<br />
with Understeer studding on the referencc cars. See<br />
Table 4.<br />
Paired comparisons of the acceleration assessments ar<br />
and a,, betwccn Under- and Overstcered studding in<br />
these sessions contradictcd the paradtlxical rclationship<br />
between thc average values. <strong>The</strong> qualitative rcsults after<br />
matching were as expected from commt)n-sensc: Better<br />
studding at the driven wheels (Ovcrstecred in Front<br />
Driven cars) gave greater accelcration values in morc<br />
lhan '|OVo (3-5 of 48) of thc available data pairs (8<br />
sessions x 2 drivers x 2 acceleration values x 2 brakc<br />
configurations = 64 minus 16 sensor drop-outs make 48<br />
pairs).<br />
Such sources of bias should be investigated before<br />
overintcrprctin g di fferences between avera ge values over<br />
scveral sessions. Thcrefore, it is clesirable to continue the<br />
analysis and to check some of the primary evaluations in<br />
this paper with methods and variables, that ilre insgnsitive<br />
to bias due to ice friction variation bctween<br />
sessions.<br />
One must also bear in mind that the discrimination<br />
here between Front and Rcar wheel drive may be misleading,<br />
sincc the cars in question (Volvo 440 and Volvo<br />
740 respcctively) are diffcrcnt in many other ways' as<br />
wcll, see Table l. Particularly when comparing the deceleration<br />
levels (d*. in Table 5), it may be intormative<br />
to know that the 440-model has a valve in the hydraulic<br />
brake systcm allowing for greatcr friction utilization at<br />
thc rear wheels (before front wheel locking) on mcdium<br />
slippcry surfaces. No such function has been includcd in<br />
the 740 model, due to the emphasis on stability in its<br />
design philosophy.<br />
Comparcd to the Front or Rear wheel drive issuc,<br />
these details in the brake systcms may be more decisivc<br />
of the contradiction between Table 5a and Table -5b<br />
regarding the qualitative difference bctween Oversteer<br />
and Understeer in ABS deceleration enhancement<br />
(Ru,*r). Though the differenccs may lack statistical<br />
significance, the Ro** is greatcr for the Oversteercd<br />
8r8<br />
configuration in the 440-model, while the 740 benefits<br />
morc from ABS with Understocring tyres, This is<br />
consistent with the 440-140 differcncc in brakc force<br />
distribution. Wilhout ABS the 740 will lock up ils I'ront<br />
wheels at fl decelcration which is more inferior to the<br />
lock-up limit of the rcar wheels than in the 440-modcl.<br />
Nevertheless, thc average deceleration valucs differ<br />
substantially betwccn Basic- and Mitxi-studdcd tyrcs, as<br />
should be expecled. Thc difference seems signil'icant<br />
both statistically and practically, since the lveragc drivcr<br />
improved the decclcration with more thfln 20 7o when<br />
changing from Basic- to Maxi-studded tyres on all<br />
whccls.<br />
Driver Brake Release (Jpon ABS Vihratittns, Accidenl<br />
Risks and Driver Education<br />
During preparation and training of the subjccts, many<br />
drivcrs bccame surprised and released the brlkc ltcdal<br />
whcn they perceivcd lhe noise and vibration lrom the<br />
activatecl ABS. According to driving tcflchcrs at Swedish<br />
skidpads, this reaclion and litck of senscrry cxpcrience is<br />
comrnon cvcn among ABS clrr owllers. Suitilble inforrnation<br />
and training might therefore be offcrcd to drivers<br />
who rcnt, borrow or buy a car with ilnti-lock brakes.<br />
Thc ABS surprise rcaction and spontartcous brake<br />
releases in cmcrgcncy situlttions may have contributcd to<br />
accidcnts. Pcrhaps that has contrihuted to the negativc or<br />
lack of positive effect on salety from ABS, which has<br />
been reportcd by a few invcstigators. Howcver, Bichl'<br />
Aschenbrenner & Wurm (1987) intcrpret their negativc<br />
results as A support for Wilde's risk homeostasis<br />
"theory" (sincc it cannot bc gcnerally frrlsificd, it is<br />
doubtful if it should bc considered a scicntific theory).<br />
Risk homeostilsis meilns that drivcrs keep the accidcnt<br />
risk at a constflnt level by increasing speed arrd by<br />
changing<br />
"towards<br />
a riskisr or less cautious manncr of<br />
driving" (OECD, 1990), when they becomc aware of<br />
irctivc safcty improvements, c.g. ABS.<br />
Though Bichl et al (1987) only were unsuccessful in<br />
thcir attcmpls to find significant el-fects flonr ABS on the<br />
accident risk (no cffect found = "llcgative<br />
results"), the<br />
risk homcostasis idea sccms to convince some pcople<br />
that ABS is worthless-as well ils mirny othcr driver<br />
supporting meitsurcs intended to reducc thc accident risk.<br />
Such a destructive attitude may be encouraged by belicf<br />
in risk homeostasis, but is questioncd front a scientific<br />
point of vicw by Stottrup-Hanscn et al (1990).<br />
Accorcling to Aschenbrenncr (199 l), data from their<br />
study (Biehl et al, 1987, further evaluatcd by Aschenbrenncr<br />
ct al, l99l) "indicatc<br />
ttrat ABS drivers had less<br />
accidents whcn they used the brakcs and more accidents<br />
in which thcy did notbrake tt all, e.g. losing one's way<br />
in an icy curve." This statcment put doubts into the<br />
above mentioned assumption that spontaneous brakc<br />
relcascs in etnergency situations may have contributed to<br />
accidents. Neverthcless, it also points at a considerable<br />
safety potenti{rl o[ ABS, which rlay bccome better
eflcctcd in accident statistics, if drivers are effectively<br />
informcd of the limitations of ABS-and trained in<br />
utilizing ABS (even in icy curves).<br />
<strong>The</strong> potcntial safety gains of ABS education lnd training<br />
is clearly demonstratcd in driving expcrimcnts by<br />
Priez et al (199 l). Trained drivers wcrc about twice as<br />
prone as their untrained matches to behave adequatcly in<br />
a surprising simulated emergency (car durnmy autornatically<br />
pulled out at a crossing with restrictcd visibility).<br />
<strong>The</strong> "training consisted of a theoretical part explaining<br />
the objcctive and functioning of the ABS systcm, as well<br />
as fl practical part involving demonstrations and avoidance<br />
exercises. This training took place two months<br />
beforc testing" and occupicd the participilnts a half-day.<br />
In a double-blind classification of the driving<br />
behaviour of thcir subjects (taxi drivcrs in Munich),<br />
Biehl et al (l9tt7) found thilt thcir observers (acting as if<br />
they were ordinary passengers to thc taxi driver) had<br />
judged the average driver behaviour ils lcss cautious with<br />
ABS in all l8 variables taken into account. Though it<br />
was possible to identify an ABS car by the control light<br />
in the instrumcnt panel, the obscrvcrs we re not inforntcd<br />
whethcr the car had ABS or not. Neilhcr wcre they told<br />
that thc study dealt with thc influence from ABS (as far<br />
as has bccn interpreted from Aschenhrenner et al, l99l ).<br />
<strong>The</strong> conscientious invcstigation by Aschenbrenncr-<br />
Biehl-Wurm offcrs strong evidence that drivcrs bchave<br />
more risky duc to unrealistic expectations on the safcty<br />
improvements with ABS. Howevcr, though the subjccts<br />
were professional taxi drivers, thcy had not received any<br />
specific education on ABS. <strong>The</strong> question is if adcquate<br />
training might improve safcty in real traffic also-as on<br />
thc test track for Priez et al (1991) mcntioned above.<br />
Data from the present study are encouraging in this<br />
respcct. Though our driver subjects rcccivcd only very<br />
short and improvised<br />
"training," they pcrformcd better<br />
with ABS (sec above)-and through their speed sclcction<br />
in the Combi manoeuvre (scc bclow) lhey did not cxhihit<br />
any grcater self-confidcnce with ABS than without.<br />
Since they may be due to the scssions' training cffcct,<br />
a couple of differences will be pointed out hcrc between<br />
the first and the last Combi test made with thc driver's<br />
own car. In the introductory tests of thc scssion, 23<br />
drivers succceded in stopping their own car bcl'ore the<br />
left lane "end" (X= l60m in Figure 3), but in the<br />
corresponding test at the end of the session only three<br />
(3) drivers succeeded. Data were available for 40 drivers<br />
in this comparison. <strong>The</strong> dctflils behind havc not yet heen<br />
investigated, but probably thc drivers were morc able to<br />
accelerate and reach a higher spced with thcir car at the<br />
end of the session. This may hrve undesirahle effects tln<br />
traffic behaviour and safety. On the other hand, the<br />
deceleration performance increased for a majority of thc<br />
drivcrs. A simple count revealed that 2l of 36 drivcrs<br />
(whcre data were complete in this respcct) achieved a<br />
greatcr deceleration valuc with their own car after thc<br />
reference csr tcsts than before.<br />
Sectlon 3: Technlcal Sessions<br />
One apprehcnsion concerning ABS was rcinforced<br />
during the author's own lcst driving a frttnt whccl drivcn<br />
car with both ABS and Autonurtic Spin Hcduction<br />
(ASR). A rear whccl skid dcvelopctl to unrccovcrithlc<br />
whcn thc ASR prcvcntcd spinning of the lront whccls'<br />
<strong>The</strong>n it becamc desirable to lock up all whecls tnd kcep<br />
the car motion slraighl to shy on thc pilth. llowcvcr,<br />
ABS made that impossible and thc car continued turning.<br />
Finally, it wcnt llackwards into a stack o[ hard srow.<br />
Similar properly damage has bccn reportcd front skidpad<br />
driving wilh ABS buses. In lr critical situation on the<br />
road it may also be more injurious to crash in I side<br />
impact aftcr an AIIS supportcd yaw nlotion than lo luck<br />
up all whecls into a frontal impact. Pcrhaps an onlcrgcncy<br />
lock-up function should lre availablc in ABS clrs<br />
or automatically triggered whcn thc skid (sidcslip anglc<br />
and yaw motion) excecds llrc rccoverablc lcvcl,<br />
Speed Selertion With and Without ABS<br />
According to risk horrtcoslltsis, drivcrs should drivc<br />
faster with ABS than without in thc Cornbi Manocuvre,<br />
since they werc cxplicitly told by thc instruclor if the<br />
ABS was switched on or off hefore thc tcst, In order to<br />
test this hypotlrcsis, thc records l'rom Speed Scnsor 'S'S2<br />
wcrc evuluutcd. Etch driver madc 4 Conrlli tssls with<br />
ABS and 4 tosls without (onc tcst pair per referencc car).<br />
<strong>The</strong> speed lcvcl at SS2 was mo$tly lllout 70 knl/lt with<br />
driver avcragcs ranging frottt 62 krn/tr (l'or thc Basicstudded<br />
Rear whccl driven cars) to 75 krn/h (for thc<br />
Overstcered Fr
13th lnternatlonal Technlcal Conference on Experimentel Safety Vehicles<br />
pointing at the potential of more precise knowledge and<br />
of continued efforts from cxperienced safety promoting<br />
prolcssionals.<br />
Results and Discussion: Double Lane Cfrange<br />
Manoeuvre<br />
Lo ss -of-C ont rol S t ali sti c s<br />
Sincc lane-marks were hit in only 3l of 416 Combi<br />
tcsts, the lane keeping tilsk seems to havc bccn compflratively<br />
simple for this drivcr group, as was intcnded<br />
when the Combi test track was outlinecl. <strong>The</strong> Double<br />
Lane Change (I)LC) Manocuvre, on the other hand, was<br />
designed to challenge the lateral stability and skid<br />
recovery performance to a grcatcr cxtcnt.<br />
To distinguish tests with different degrees of drivcr<br />
control, a Loss-of-Control Scors (LCS, with four levels<br />
from 0 to 3) was determined by thc onhoard instructor or<br />
by the trackside observers and the tcst rnanagcr.<br />
0 No steering wheel corrections and no hitting of ltne<br />
marks gavc LCS 0.<br />
I Stccring whcel corrcctions only gave LCS I (determincd<br />
subjcctivcly by the onboard instructor).<br />
2 LCS 2 was recorded if (tracksidc obscrvcrs discovered<br />
that) lane-marks wcrc hit without a complete loss of<br />
control.<br />
3 LCS 3 means that the driver tost control and thc car<br />
lcft thc lane complclely.<br />
In 348 normally recorded DLC tests with the reference<br />
cars, 94 tests (27%) resulted in Loss-of-Control (LCS=<br />
3). For individual drivers the Loss-of-Control ratio<br />
vnricd from 0 of 9 tests to 5 of 7 tests 0l%).<br />
However, the LCS statistics should not be used alone<br />
for ranking the drivers and for asscssments of thcir<br />
individull skills. Eight drivers hld no LCS 3 at all, hut<br />
four of them drove slower than demanded-resulting in<br />
smallcr adhcsion utilization latcrally thirn what they had<br />
longitudinally in the Combi tests. When skidding to the<br />
left in thc left lanc, othcr drivcrs tricd lrardcr than<br />
normally to avoid thc "oncoming<br />
car" lane-nrarks (C 105,<br />
110, etc in Figurc 3). Thcir prolongcd stccring to the<br />
right made the clockwise yaw morc pronounccd and<br />
incrcased the risk of an LCS 3 outcorne (leaving thc<br />
lanc). Drivers who countersteered earlier to the lclt had<br />
an easier task to avoid LCS 3, if they acceptcd LCS ?<br />
and deliberately run over thc ccntrc lanc-marks in the<br />
vicinity of no.Cl0.5.<br />
When ranking cars and tyre studding configurations,<br />
it is also important to consider differenccs in spccd and<br />
manoeuvre severity. With a "hcttcr" car, thc test manager<br />
could rcquest a Brcat$r speed in the first DLC run of<br />
each driver. <strong>The</strong>refore, a greater pcrccntagc of tcsts with<br />
complete Loss-of-Control (LCS 3) nray be justiticd for<br />
tyrcs with greater adhesion. However, no such distinct<br />
statistical relationship hetween speed and Loss^of-<br />
Control percentage has bccn found, scc thc discussion on<br />
Figure l0 bclow.<br />
Anyhow, thc tcst proccdure aimed at speeds which<br />
wcrc on both sides of thc bordcr of losing control for<br />
each car-driver combination. At thcsc spccds it rnust<br />
have been possiblc [o rrlovc lhg citr laterally l'ronr thc<br />
right to the left lane, il'thc tcsl should be considercd in<br />
this cvaluation. A similar motion rnly bc initiated by the<br />
drivcr in traffic, as well. Irrcspcctivc of thc spced level,<br />
it sccms safety-relevant to dctcrminc thc liksliness of<br />
such a possible manoeuvrc lcading to Loss-of-Control.<br />
Thcrcforc, LCS statistics has been computcd to illustrate<br />
thc tyre influence on the control propcrtics of the<br />
rclcrcnce cars (A-D). See Table 7.<br />
Table 7. Number of Double Lane Change Tests Grouped<br />
into Two Loss-of-Control Score (LCS) Levels<br />
7<br />
3<br />
J<br />
7<br />
E<br />
9<br />
l0<br />
tl<br />
l?<br />
IJ<br />
l4<br />
t5<br />
ft{k<br />
C D<br />
ti It<br />
+z +I<br />
4t 39<br />
v +r<br />
n n<br />
c&D (+2) +J<br />
41 09<br />
P) +2<br />
19 l3q<br />
D C<br />
FMt<br />
+l +?<br />
25 3l<br />
+t fl<br />
57 62<br />
c&D ll +J<br />
l? d9<br />
lJ tt<br />
9? t39<br />
E A<br />
l4 l0<br />
o + 2<br />
l0l 30<br />
+6 +f<br />
6+J<br />
{LCS{r)<br />
lntl Cn[?<br />
ll l0<br />
58 67<br />
i l s<br />
TE IIO<br />
lI x<br />
14 t9<br />
12 11<br />
f l {<br />
(KS-Jt<br />
ll ?<br />
t 0 9<br />
? t i l<br />
o? E<br />
6f<br />
53 ilo<br />
z$<br />
l0 2l<br />
2 t i l<br />
1 4 6<br />
lt 12<br />
25 l8<br />
72<br />
6<br />
t? 2l<br />
39 !9<br />
rcs-l ($d d.E rtr.elud. bilr,<br />
vhE |ffi of6.6E. Sp.d<br />
*ryD scF nulnrHinilin$<br />
Scili.nr 9.lS only. Sbd.d Drc-<br />
JJ* I*<br />
!!E 2l* Ar !h. but dy tuuM<br />
24% 25%<br />
lfE l{i Suh of boft rh. (D!h !Y.ihbl.<br />
Itl<br />
d4) ils<br />
J:N<br />
G4 ?1*<br />
sca'nilN l-ln, AttNvrd srxildr!{<br />
Ar rbov+ bur ody Frcd h.cl<br />
Su.r ofhoh rhdE. (D$ rv.ll$I.<br />
Ssasiur' l-8 {trlr $tril{nl PLC-<br />
4t* 24*<br />
4fi 39% A, rh.v. hutOtrly Fmilkl<br />
tt* 4ti<br />
fl* 29* Suh of bd !bd.. Elb .vlibbL<br />
Drk usr thilr ill sqr$3.<br />
1t* tt* Appd.d Sbdld DLC{!rk.<br />
#E (30) ^r !bov. hut only Fhot S.d<br />
t2x t?*<br />
&* 1Zt) Suh olbd !bd.. Dlh.v!il.bL<br />
4Jt 19<br />
6I Zn {fr 0r)<br />
4J* t9*<br />
l?l 4<br />
#* l9*<br />
se*iln's ll-?t D'{y sr{il{iil<br />
DLC-Erlr. (rE !v!ihbl..t l.!il<br />
A{ riw+ sq&d<br />
ui6 S&nr<br />
l-8 lrd tutu.dry&.rtu|<br />
Driv. /.rrbr it sr !s-16<br />
^r ihnrc ddn'ddcd *'s ril<br />
nrpru!il &dil Dlcrftrs. Ndu:<br />
Bold lext indicate the most suitable rows for comoarisons<br />
between different combinations of Reference car (Front Wheel<br />
Drive; Volvo 440 & Rear Wheel Drive: Volvo 740) and Tyre<br />
Studding Configuration. Undelliled pelqentages are repeated<br />
later (within parentheses). When both obstacle marks (C70 & C80<br />
in Figure 3) were hit, the test had to be disapproved for Lateral<br />
Acceleration Assessment. lf such tests a16 rncluded, their<br />
numbers appear in ltalics,<br />
Whcn ttrc Loss-of-Conrrol Score is dichotomiz.cd to<br />
either LflS J or snrallcr (LCS 0-2). distinct diflerenccs<br />
ilppear betwccn thc Ovcr- und Undcrsteered configura-<br />
tions. While cornplete loss-of-control occurred in only<br />
four (13 7o) ol' thc 30 approved DLC-tests with Undcrstccring<br />
tyrcs (all four were rear whecl skids cnding in<br />
spin-out), the Oversleering tyrcs cxhibit LCS 3 in 84 (41<br />
%) oI 205 Dl-C-tests, sce row l-5 in Tahlc 7. Howovcr,<br />
row l3 shows thtt only 14 Oversteering DlC-tcsts ilre<br />
fully comparalrle to the 30 Undcrstccring oncs (i.e. with<br />
Front Wheel Drivc, rccording in scssions l9-26, and<br />
wilhout intcrvening Pedal tests which unirrtcntionally<br />
excluded about l-5 such normal DLC tests l'rorn cvaluation).<br />
If one counts Loss-of-Control (LCS=3) tests together<br />
with r/isapproyrrrl tests (becausc ol'Early Plow-Out and<br />
hitting holh obstirclc marks C70&C80, itulics in '[atrle<br />
{l
7), the "failure* percentages increase, but the rank order<br />
remains the same in most clf thc comparisons in Table 7.<br />
Figure 5 presents some of the percentages from Trblc<br />
7: row I & 2 (Basic Studding), row l0 & ll (Ovcrstccring<br />
and Maxi), row l3 (Understecring). Thc confidcnce<br />
intcrvals in Figurc 5 are estimated from Binomial Parameter<br />
tables (Dowdy & Wcarden, l99l).<br />
While Ovcrstccring tyres result in inl'erior handling in<br />
most of the Tablc 7 comparisons, Maxi studded tyres on<br />
all four wheels result in substantially grcatcr Loss-of-<br />
Control ratios for thc smaller FWD cars (A&B) than for<br />
the larger RWD cars (C&D). See row pairs I & 2 or 7 &<br />
8 merged on rows 4 & 5 (versus Basic Studding) and on<br />
rows l0& I I (versus Oversteering Studding). In addition,<br />
it appears from Figure 8 that the averilge milnoeuvre was<br />
less severe with the smallcr cilr typc A&8. which<br />
emphasizes the infcriority of its control proltcrtics.<br />
Thc infcriority in stahility of the A&B cars in the<br />
Loss-of-Control statistics (Table 7, Figure 5) is remarkable,<br />
since their smaller width puts less demand on<br />
lateral motion and litterrl accelcrirtion in tlrc DLC<br />
mflnoeuvrc than lor car C&D. In Figurc tt&g it will bc<br />
dcmonstratcd that thc latcral accclcration assessmcnts at<br />
transition to Loss-of-Conl.rol wcre smallcr {or thc FWD<br />
cars A&B in comparison to car C&D in the sanrc<br />
sessiorrs Nevertheless, thc FWD car inferiority in thc<br />
tcsts may bc valid and safcty-relevant on public roads, as<br />
well. See thc section below on Hazards with Front Bias.<br />
I r.*** n *nr r*.*- . "*;-- ;;,-;; -;;;l<br />
l _<br />
lm*<br />
SE<br />
80fr<br />
70t<br />
ME<br />
50fr<br />
10t<br />
30F<br />
20fr<br />
lofr<br />
o*<br />
Approximate 95% confidence intervals for 'failures.. Column<br />
groups for Car types: AaB; C&D; all types A-D, Separate columns<br />
for Tyre Studding config: E; Ovr; Bas; Max: Und.<br />
Figure 5. Proportions of "Failures" (Loss-of-Controlor<br />
Early Plow-Out) end "Successes" (Maintained Control)<br />
in ths Double Lane Change Tests<br />
Assessrnenl of Lateral Accrlerttittn from Speed and<br />
Distances<br />
In this kind of driving experiments, crash avoidance<br />
capability is often determined as a threshold spccd (or<br />
similar physical quantity), which only "bcttcr" drivcrvehicle<br />
combinations can cxceed without losing control.<br />
To malie the results nlore generirl and possible to judge<br />
for other investigltors, we aimcd at quantitics comparativcly<br />
independcnt of the test path geometry. In both the<br />
Combi and the Double Lane Clhange tests it was also irttportant<br />
to make the results and their varirncc inscnsitive<br />
$ection 3: Technlcal Sessions<br />
to fluctuations in ice friction, which should be expected<br />
in a three week outdoor tesl progrirm.<br />
Thcrcfore, we dcsigncd the experiments for assessments<br />
of lateral (and longitudinal) accclcrations and<br />
ratios thereof, such as in Table 4 & 5. A typical value of<br />
the lirtcral accclcrrtion in the Double Lune Change<br />
manoeuvre may bc asscsscd frotrt the path geontctry and<br />
from the Spccd Scnsor rccordings. A Driver rrodsl<br />
(Approximation) l'or Vchiclc Invcstigation by conrputer<br />
Simulation, DAVIS, dcvclopcd by Strandbcrg (1972),<br />
determines the latcral ilccclcriltion from lhe spccd (v,<br />
assumed to be constant durins the nttnocuvrc) trrd thc<br />
followin g pa-ram ctcrs:<br />
L (ideal) Manocuvrc Lcngth is del'ined as twice the<br />
Iongiturlinal distuncc from tlrc bcginning of left<br />
motion in right lrnc to lhc ccntrc ol the "right lane<br />
obstilclc" (whcrc thc lltcrll trtotion will change from<br />
lcl'twrrds to rightwlrds in u synrmetrical DLC rrhout<br />
the l0 nr long blocking of thc right lrne), From<br />
wheel trilcos on lhc icc. thc valuc L=80nr has heen<br />
used in thc cvaluations hcre. (Even if the<br />
longitudinrl "gatc" was 60nr, see Figure 3, the<br />
liilcrll displacemenls are very slnall at the ends of<br />
rhis rritjccrory.)<br />
Y laterul nrotion rrmplitude needed to avoid hitting the<br />
plaslic tubc marks trctwccn thc Irnes and at the left<br />
corncrs oi thc sirnulated obstaclc (C70 & C80 in<br />
Figure 3).<br />
A position of the ohstacle lanc-nrarks (distancc A to the<br />
right of thc centre line l)etweelr the marks C45 to<br />
Cl05). It varicd between ccrtain sessions (A = 0.75m<br />
cxccpt in scssions 5-12 when A =0.0rn).<br />
car width (c=l.67nt for ciu A & B, c = 1.7-5m for<br />
c;rr C & D. Drivers' own cilrs E & F schcntatized<br />
heretoc=1.70n).<br />
Hence. the reference car tests have been evaluated<br />
with four alternrlive Y-values ( I.75, 1.67, I.00, 0.92 nt),<br />
since Y = c - A. According to Stritndhcrg (l97lt), the<br />
DAVIS' peak lateral (Sideways) Accelcraliott, SA is<br />
given by Eq.7.<br />
sA=<br />
6(4 + -5n)r<br />
* tl) r t<br />
(7)<br />
It should be noted thrt the conslants Y lrnd L hnve not<br />
yet becn fitted to dilta. All SA-vllues in this papcr<br />
should thereforc bc considcred rclltivc and not tbsolute.<br />
However. it nray be possible to Inake belter ilssessmcnts<br />
of thc constants L, c, and A by using rcgrcssion analysis<br />
with thc corlputer recorded acceleralion dtta l'ront ciu D,<br />
speed scnsor data. and Eq. 7.<br />
Even if the constitnt L rnd thc paranteter Y are intccurirte<br />
dcscriptions of an individual lcst lrqcctory, thcy<br />
Quantity (through Eq. 7) the cffcct front speed on lhe<br />
laterill acccleralion nccdcd in rn an idcal manocuvre.<br />
And if thc spacc givcn by a slnaller citr widlh (c) or by<br />
a smallcr obstacle (greater A) is bcttcr utilized in one<br />
821<br />
ii
lSth lntematlonal rechnlcal conference on Experlmental safety vehlcles<br />
test than in another, Eq. 7 offers an optimal-manoeuvre<br />
reference expressed as a well-known physical quantity<br />
(peak acceleration) which may be given in a standardized<br />
unit (here m/s').<br />
<strong>The</strong> smaller SA-values achieved at a certnin speed<br />
with cars A&B due to their smaller c- and Y-measures<br />
compared to cars C & D may then be considered unfair,<br />
since smaller car dimcnsions contribute to reduce the<br />
DlC-manoeuvre severity even in real traffic situations.<br />
Nevertheless, a greater SA-value reflects a more<br />
demanding manoeuvre when different tyrcs or drivers are<br />
compared from tests with the same type of car.<br />
Lateral Acceleration at the Transition to Loss*of-Control<br />
In the last mentioned respect, the crash avoidance<br />
capability for each driver has been quantified through the<br />
maximum SA-valuc achieved without completc Loss-of-<br />
Control (SAod and through the minimum value where<br />
the driver lost control (SAr"d. Referring to thc Loss-of-<br />
Control Scorc levels in Table 7, these two SA-values (if<br />
both exist) have been determined as follows for each<br />
combination of driver, Studding configuration and car<br />
type<br />
SAo* = driver-MAX(SA with LCS < 3)<br />
for onc car or a group of cars (8)<br />
SAr" - drivcr-MlN(SA with LCS=I)<br />
for one car or a group of cars (9)<br />
Figure 6 illustrates that most drivers lost control in a<br />
less severe manoeuvre than in their "best" one with<br />
maintained control. This indicates that the test managcr's<br />
speed demand was reasonable and thirt it may be worthwhile<br />
to elaborate on the influencc from parameters in<br />
cars and tyres. <strong>The</strong> possibilities to dcmonstrate the<br />
importance of such parameters are noticeable and might<br />
be used in driver education.<br />
3.6<br />
2.5<br />
sA tlcl a<br />
{o/r2l l 5<br />
I<br />
0.5<br />
0<br />
o o's t<br />
*l,uo*, t^,',r,<br />
lncludee all cars A-E, where the width c= 1.7m lor Eq. I was<br />
made to pattern for driver's own car E). Smallest valus (SAL.)<br />
from tests resulting in Loss-oFGontrol versus greatest velue<br />
(SAon) from tests with maintained control. Line y = x for relersnce.<br />
Plot on x-axis for drivers with no LoC test.<br />
Flgure 6. Each Drlver's Pair of Leteral Accelaration<br />
Extrcme Values from All Stendard Double Lane<br />
Change Tests in the Sesslon<br />
Taken over all drivers and sessions. the mean values<br />
of the manoeuvre $everity quantities (defined in Eq. 7-<br />
13) do not differ much more between studding configurations<br />
than what may be expected from random variation.<br />
822<br />
2'5<br />
One clear-cut exception has been found, though: <strong>The</strong><br />
average driver lost control in RWD cars at less severe<br />
manoeuvres with Basic Studding (SALC= l.3mls2) than<br />
with Oversteer Studding (SALC= l.9m/s') or with Maxi<br />
Studding (SArc= l.$m/s?). <strong>The</strong> Basic Studding was<br />
inferior also with the FWD cars. Sce Table 8. <strong>The</strong> rear<br />
biased weight distribution in ciu D comparcd to car C<br />
may have contributed to the great values with Oversteer<br />
studding (only car D) in comparison to the Bilsic<br />
Studding, whcre car C dominated the RWD tests.<br />
Table 8. Greatest Lateral Acceleration with Maintalned<br />
Control (SAo*) and Smallest with Loss-of-Control<br />
(SAr") for Different Combinations of Feference Cars<br />
and Tyre Studding Conligurations<br />
cs lyrs Stsddiq<br />
(cf- Trblc l&4) (ct Tsble 3)<br />
A&B (FWD) Overster<br />
A&B Mili<br />
A&B }tasic<br />
A&B Tlnderc+r<br />
D not C (RWP)<br />
c&b<br />
80ftc & 20*D<br />
Mean vaiues over all drivers in normal Doubfe Lane Chang€ tests.<br />
Std.err. (standard €tror = sample standard deviation divided by<br />
fn) designates usual Bstimate of standard deviation of the mean.<br />
Paired comparisons in Table 8 (as well as in the figurcs<br />
with 9570 confidence intcrvals) may reveal several<br />
"significant"<br />
differences on the 57o lcvcl. However, the<br />
number of possible comparisons is too great for this<br />
lcvcl and the likelihood of mass-significance must be<br />
considcrcd to avoid misinterpretation of thc results.<br />
When trying to rank order the cars, their cffcct is<br />
obscured by the great "noise" lrom driver and session<br />
variances in SAo*. This is illustrated in Figure 7, whcre<br />
SAn* values for each combination of driver and rcfcrence<br />
car A,B,D is plottcd yersus SAOK fbr car C with<br />
the same driver (but only from session l-8, whcrc the<br />
studding conliguralions were unchanged, see Table 4).<br />
<strong>The</strong> valucs for Car C (with Maxi studding) were selected<br />
as the indepcndent (x) variatlle, since thcy were the<br />
greatest with most drivers.<br />
gAtoKl<br />
(hlrA<br />
Csrs<br />
A,A,D<br />
3<br />
2.5<br />
1<br />
0,5<br />
Oversteer<br />
Mari<br />
Basic<br />
iAOK (n/sr) $AOR<br />
Ues vilP t^u?l<br />
l.5l 0.09<br />
t.48 0.08<br />
t.40 0. r I<br />
td.o ndK<br />
t.80 0.06<br />
r.84 0.0E<br />
t5R Ot6<br />
0<br />
0 0.5 | t.5 2 2.6 3<br />
Clr C Mrxl Sruddrd SAIONI tfi/rzl<br />
tA16 (n/*2) sALc $td'n<br />
UHvalue an/sz)<br />
.75 0.09<br />
.95 0.12<br />
,5r 0.22<br />
.6E 0.14<br />
L94 0.10<br />
1.80 0. r7<br />
t_30<br />
022<br />
SA0K-values from session 1-B for reference car A,B,D plottsd<br />
versus SAo* for car C with same driver. Plot on x-axis<br />
corresponds to loss-of-control in drivers' all DLC tests with that<br />
car.<br />
Figure 7. Sixteen Drivers' Greatest Lateral<br />
Acceleration in Double Lane Change Tests with<br />
Maintained Control (SAOK in Eq. 7 & 8)
<strong>The</strong> differences in SAo*-level between tyre studding<br />
configuration cannot easily be distinguished only by<br />
comparing their mean valucs over the 16 drivers. <strong>The</strong>ir<br />
confidence intervals overlap considerably, as can be secn<br />
in Figure 8. However, the resolution increases, if differences<br />
in SAo* values are calculated for each driver and<br />
averaged. Thcn thc Maxi-studded cars may be considered<br />
"significantly"<br />
superior to the Oversteering oncs, since<br />
the lower confidence limit of their average within-driver<br />
difference is greater than zero. See Figure 8, also<br />
exhibiting more pronounced differences between the cars<br />
A&B and the larger RWD cars C&D. Even if the car A<br />
valucs are extended with up to 9Vo by assessing its width<br />
equfll to that of car C in Eq.7, the differences appear to<br />
remain.<br />
2.6<br />
2<br />
gAtoH 1.5<br />
(m/rzt I<br />
0.5<br />
o<br />
Grouping between Maxi or Oversteering Stud configurations;<br />
between Car A,B (FWD) or Car C,D (RWD); and wirhin.driver<br />
Differences. Mean values over drivers in sessions 1-8 with gE %<br />
conlidence intervals.<br />
Figure 8. Driver's greatest lateral acceleralion in DLC<br />
tests wlth maintained conttol, SAo*<br />
Ratios Between Lateral and Longitudinal Accelerailon<br />
Whcn considering the ratio between the DLC lareral<br />
and the Combi longitudinal accelerations, the differences<br />
also seem distinct between the two reference car types,<br />
see Figure 9. <strong>The</strong> within-car variation of SAo* between<br />
drivers and sessions is evidently alrnost neutralized when<br />
one divides the lateral acceleration with the longitudinal<br />
one. Compare Figures 7 &. 9. <strong>The</strong> renraining and clearcut<br />
difference between the two car types nray be partly<br />
due to stud protrusion deviations and to the nonlincar<br />
functional relationship between wheel load and friction<br />
of studded tyres on ice, which will be commenred in the<br />
last section.<br />
nATTOS<br />
2.5<br />
lrraad ,<br />
l<br />
ot"d.d<br />
6<br />
b Y r<br />
.o"e.O.s<br />
EC.<br />
0<br />
hd fu MO trf C- ..rA F.rD rE<br />
ff ED ditr Mrn Mrn affi tur fu. dtr.<br />
tud"*dEiil: :ilHH:#<br />
See ratios R*o* and Fl..o* in Eq. 10 & 1 1. Car mean values over<br />
drivers in sessions 1-8 with 95% confidencs intervals.<br />
Figure L LateralAccelerailon Dlvlded by Deceleration<br />
(d-.o) ot by Forward Acceleration (8..o)<br />
Sectlon 3: Technlcal $esslons<br />
<strong>The</strong> mcntioncd ratios may bc exprcsscd ts follows<br />
according to the definitions in Eq. 4*5 & 8-9. <strong>The</strong><br />
controlled lateral-backwards acceleration ratio is a<br />
metsure of the mrximum severity of an evirsive<br />
manoeuvre in relation to the current deceleration capability:<br />
o - sAo*<br />
"uox - n-<br />
<strong>The</strong> controlled latcral-forwtrd accclcrtlion ratio is a<br />
measure of thc maximum scverity of an cvasive<br />
manoeuvre in relation to the curreltt acceleration capability:<br />
""ox<br />
froo* = (l l)<br />
a<br />
<strong>The</strong> uncontrolled lateral-backwards acceleration ratio is<br />
a measure o[ the minimurn rnflnocuvrc scvcrity which lcd<br />
to Loss-of-Control in rclirtion lo lhc currcnt dccelerttion<br />
capability:<br />
.sA.._<br />
"sdrr R = ' ' '<br />
T<br />
(10)<br />
(12)<br />
<strong>The</strong> uncontrollcd lateral-forwrrd acceleration ratio is ir<br />
meilsure of the minimum rnanocuvrc scvcrity which lcd<br />
to Loss-of-Conlrol in relation to the current acceleration<br />
capability:<br />
sA,-<br />
Rr,tc = (13)<br />
n:<br />
Statistical Rtlationshilt Betwetn Sprrd and<br />
Lo ss-of-C o nt r o I Li ke line ss<br />
Since better tyres allowed for higher speeds, a great<br />
Loss-of-Control percentage does not ncccssarily mean<br />
poor handling qualities. <strong>The</strong>refore, several plots have<br />
been mude in pursuit for a positive correlation betweon<br />
thc tcst fitilure pcrccntags and spccd (quantificd through<br />
various normalized variables based on Eq.7-13). However,<br />
with our testing procedures and criteria for speed<br />
demand. tyre Studding and Car type (.such a.s in Figure<br />
5), appear more decisive of the LoC likeliness thiln their<br />
differences in speed ilnd manoeuvre severity, see Figure<br />
10.<br />
Nevertheless, Table 8 dernonstrate that th. gr*ut*rt<br />
possible speed in an evasive manoeuvre was lower with<br />
Basic Studding than with Ovcrstecr Studding, while<br />
Figure -5 illustrated the distinct inleriority of Oversteer<br />
Studding when it cornes to driver control. A qucstion<br />
which remains to bc answered is: what happens on the<br />
road to the average driver at the same speed'l Will<br />
Oversteering properties rcsult in unncccssarily severe<br />
manoeuvres provoking spin-outs to a greilter extent than<br />
with Basic Studding properties'? Or will the steerability<br />
offered by the superior fronl wheels in an Oversteering<br />
823<br />
"{<br />
t<br />
.!<br />
'.!<br />
,':<br />
l<br />
'j<br />
.i<br />
,j<br />
I<br />
..1<br />
.ri<br />
4<br />
-l<br />
_ri<br />
4
lSth lntefnetlonel Technlcel conference on Experlmental safety vehlcles<br />
car just be utilized in emergencies, that arc impossiblc to<br />
cope with in a Basic Studdcd car?<br />
It may be difficult to design experiments for valid<br />
investigations of drivcr behaviour from this viewpoint,<br />
but it would be clarifying to apply the cascrcontrol<br />
method from epidemiology to assess the relative risks<br />
associated with tyre differences within cars. See<br />
Schlesselman (1982), Joncs & Stein (1987), Strandberg<br />
(1991). Even if only minor cffccts may result from a<br />
conscious and safety-promoting positioning of tyres, the<br />
costs scem negligible to the individual. According to the<br />
present study, fiaffic safcty would benefit from improved<br />
knowledge and more extensive driver education on the<br />
substantial differenccs between cats and tyres in<br />
handling propcrties.<br />
z<br />
1.8<br />
1.6<br />
A...1.2<br />
EAILOI 1<br />
0,8<br />
lm/r?l 0 6<br />
0.4<br />
o'2<br />
o<br />
F@<br />
q<br />
2.5 As<br />
sw<br />
t.6<br />
l b v<br />
0,5 he-<br />
, *,J;l;;Hffi ffi"ffi #* **10,"n ",.<br />
combinations.<br />
Figure 10. Three Manoeuvre Severity Quantities (SAt"<br />
in Eq.9 end RetiosThsreolas in Eq. 12 A 13) Plotted<br />
Versus Lose-of-Control Percentages in Double Lane<br />
Change Tests with Same Vehicle<br />
Comments on Hazards with Front Bias in Wheel Load<br />
and in Stud Protrusion<br />
Considering sessions l-8 only (rows 7 & I in Table<br />
7), the car A percentage with Loss-of-Control (LCS=3)<br />
was about twice that of car C. <strong>The</strong> handling inferiority<br />
of the smaller FWD cars A & B compared to the larger<br />
RWD cars C&D, may be more duc to other factors than<br />
to the Front Wheel Drive per se. For instance, il shortcr<br />
wheelbasc detcriorates stilbility (Strandherg et ilI, 1982).<br />
Another cxplanatory factor with Srcflter potency was<br />
suggcstcd by Nordstrom (1991). Like the average FWD<br />
car, the A&B cars may have had front/rear whccl loads<br />
closc to the opposite extremcs of the Side Force Coctficient<br />
curve (SFC as a nonlinear function of wheel load<br />
for studdcd tyres on ice). According to Elgeskog &<br />
Brodd (1976) an incremcnt in wheel load of rtrout 1000N<br />
(lOokg) or more may raise the SFC by about 2-57o. With<br />
a driver and at nominal curb weight the A&B cars<br />
exhibit ahout 120kg grcater load at a front whccl than at<br />
a rear one, see Tahle 1. <strong>The</strong> front-rear wheel loads for<br />
the C&D cars differ less (about 70kg) and are on a<br />
higher weight level, which may be more distant from the<br />
$teep ascent in the f-shaped SFC-curve.<br />
Even if the numbers are small, rows l&7 in Table 7<br />
illustrate the influcncc on stability from rcar wheel load.<br />
8U<br />
0<br />
<strong>The</strong> Loss-of-Control percentilgc with Maxi Studded<br />
RWD cars was 19 7a whcn car C was used (row 7),<br />
while car D exhibits the sntallest ratio in thc wholc table<br />
(57o on row l). It mfly be statistically dubious (lrccausc<br />
known data cannot be uscd for hypothesis testing) to<br />
point out that thcse percentages are almost outsidc cach<br />
other's 957o confidence interval. Nevertheless, this<br />
differencc in Loss-of-Control ratios offcrs support to the<br />
above mcntioned explanation, since the whccl load of car<br />
D was rear biased in compurison to cilr C and to the<br />
numbers in Tablc I, mainly due to the rear-scatcd<br />
inslructor / computer operiltor.<br />
ln addition to this haz-ard in rear-light cilrs, mcilsurcments<br />
have indicatcd thilt thc average car on Swcdish<br />
winter roads hirs a greilter stud prolrusion lt thc driven<br />
whecls. In a study of 200 randonly selccted cars, reported<br />
by Strandberg (1989), the diffcrcncc was statistically<br />
significant for FWD cars. It should be notcd thtl this<br />
stud diverging phenomcnon intproves statrility with RWD<br />
and deterioratcs it with FwD.<br />
Thc protrusion increases flrstcr when driving on ice<br />
wilh grcat adhcsion utilizalion (Nilsson, 1990). In spite<br />
of the tyre contributor's careful running-in proccdurc, the<br />
stud protrusion was found to be substantially greatcr<br />
after the experimcnts than before, pilrticulilrly lor the<br />
FWD tyrcs, sec Table 2. Sincc wc did not lnove the<br />
wheels between front and rear regularly, it cannot be<br />
ruled out thilt the tyrcs on car A&ts increascd thcir<br />
adhcsion more at the front through successively greilter<br />
protrusion.<br />
However, this dcvclops in most FWD cars evcn in<br />
traffic on winter rords, whcre rear wheel skidding acci'<br />
dents with FWD cars are frequent, contrary to common<br />
belief. Official statistics indiclte thilt such instability<br />
accidents take morc livcs than loss-of-steering accidcnls<br />
(Strandberg, 1989). Though spin-outs may bc lcss<br />
common than plow outs, sicle impacts ilrc morc injurious<br />
than frontal impacts in convcnlional automobiles.<br />
In rcar wheel drivctl citls, also excessive throttle or<br />
cnginc braking may surprisc the driver with unexpected<br />
powcr ovcrstecring. One of our drivcr subjects wils very<br />
closc to a scvcrc crash into the testing basc. When car D<br />
bcgan to yaw during acceleration lor a Cotnbi manoeuvre,<br />
the driver did not relcase the throttle. Aftcr a<br />
couplc of recovered skids hc sltun out with llmost<br />
constrnt speed and hit the speed sensors beforc thc car<br />
camc lo rcsl. According to our qucstionnilirc, he had a<br />
driver's license even for hctvy vchicle contbinations trut<br />
almost no experiencc from rear wheel drive on wintcr<br />
roads.<br />
Since rear wheel skids may be controllnble (for a<br />
skillcd driver with plenty of lateral space) and less<br />
common than loss-of-stecring-at least in FWD cms,<br />
many drivers reject understecring more than oversteering<br />
properties. <strong>The</strong>reforc, drivers should be informed about<br />
these potential instatrility hazards in the average FWI)<br />
car-and onc simple remcdy (tttounting wheels with
Sectlon 3: lechntcal Sesslons<br />
greater stud protrusion at the rear). Of course such Biehl, 8., Aschenbrenner, M., Wurm, G., (1987). Ein-<br />
mounting may dcteriorate the deceleration performance fluss der Risikokornpensation auf die Wirkung von<br />
(see dmac in Table Sa) and increase the risk of under- Vehrkehrssicherheitsmassnahmen am Beispiel ABS.<br />
steering or plow out accidcnts. Hence, further accidcnt U n tirll und S ic helhe itsl'orsc h u n g S trassen verkehr. Heft<br />
analysis is needed before it should be generally 63. Bundesanstalt fiir Strasscnwesen.<br />
recommended to mount the best tyres at the rear. A suit- Dowdy, Shirley & Wearden, S., (1991). Statistics for<br />
ablc epidemiological method has been adapted to lhe Rcsearch. John Wilcy & Sons, Ncw York.<br />
routines of the Swedish police, see Strandtrerg (1991). Draper, N., & Srnith, H., (1981). Applicd Regression<br />
In follow-up tests with car D after the ordinary 26 Analysis. John Wilcy & Sons, Ncw York.<br />
sessions, we found that steerability wilh poor tyres<br />
(Basic Studding) at the front whccls could be improvcd,<br />
Elgeskog, E., & Brodd, S., (1976). Thc Influcncc of<br />
Whecl Slip Control Dynarrics on Vehicle Stability<br />
if rcar whcel skidding was initiated by a couple of small during Braking and Steering. In Braking ol' Road<br />
steering reversals before the actual DlC-manocuvre. Vchiclcs, I Mcch E Conf. Publ. 1976-5, pp. -59-68<br />
Such intentional skidding may belong morc to lhc racing (rcf. to Fie. 4).<br />
or rally course than to public roads. But it must bc Fisher, R.A., (1958). Satistical Methods for Research<br />
rcmcmbered that similar skids may be initiated unin- Workers. In J.H. Bcnnet (cd.): A Rc-issue of Statistitcntionally<br />
by any driver when it is slippery-in spite of cal Methods lbr Research Workcrs, Thc Dcsign of<br />
the car exhibiting clear-cut understeering properties in Expcrimcnts, and Satisticnl Mcrhods and Scientific<br />
molit common manoeuvres.<br />
Inference, Oxford University Press, 1990.<br />
Acknowledgements<br />
Hansson, R., ( 199 I ). Personal communication on braking<br />
systems. Volvo Car Corporation, Griteborg, Sweden.<br />
This study has been jointly sponsored as a part of the Johnsson, L., & Knutsson, K., (1973). Ficld Tcsting<br />
Swedish reseiuch and development programmc for skid<br />
training. Funding organizations are (in alphabetical order<br />
Strtistical Tcsts. ln Swedish Experimcntrl Safcty<br />
Vehicle program<br />
of the Swedish abbrcviations) Thc Service Company of<br />
the Swedish Insurance Industry (FSAB), thc National<br />
Society for Road Safety (NTF), the Swedish Association<br />
of Driving Schools (STR), the Swcdish Transport<br />
Research Board (TFB), the Nationfll Rotd Safcty Office<br />
(TSV), thc Swedish Road and Traffic Research Institute<br />
(VTI). Grants for the experiments wcre also oflbrcd l'rom<br />
Volvo Car Corporation within the Europcan PROME-<br />
THEUS programme. Substantial contributions with<br />
equipment and knowledge were supplied by Volvo and<br />
by Nivis Tyre Inc. Audi, Mazda, Saab, and Subaru have<br />
also providcd high-tcch cars, giving the members of the<br />
project group hands-on driving expericncc from disconnectable<br />
ABS, 4-Whecl-Stecring, Automatic Spin<br />
Reduction, and 4 Wheel-Drive. Valuablc and apprcciated<br />
assistancc was givcn try mcrnbcrs of thc Swedish Fedcrltion<br />
of Women's Motor Transport Corps (SKBR). Thc<br />
Tourist Office in the town of Orsa kindly actcd as intermediary<br />
to the drivers. People living in thc village<br />
Sandsjo at lake Hcmsjon stood behind the practical<br />
arrangements in spite of the short notice. <strong>The</strong>ir concern<br />
of our pcrsonnel, cquipmcnt, and activitics was a rclicf<br />
to the whole testing team.<br />
References<br />
Aschenbrenner, K.M., (1991). Personal correspondence.<br />
Hocchst, A.G., Frankfurt am Main, Gcrmany.<br />
Aschenbrenner, K.M., Biehl, 8., Wurn, C.W., (1991).<br />
Mehr Vehrkehrssicherheit durch bessere Technik?<br />
Feldtuntersuchungen zvr Risikokompensation am<br />
Beispiel des Antiblockiersystcm (ABS). Final report<br />
to Bundesanstalt fiir Strassenwcscn. In press.<br />
"Steerability During Emergency<br />
Braking," Report 4-01.<br />
Joncs I..S., & Stcin. H.S., (1987). Defcctive Equipmcnt<br />
and Tractor-Trailcr Crash Involvcrrtcnt. Insurancc<br />
Institutc for Highway Safety, 1005 N.Glebe Road,<br />
Arlington, Virginia 22201, USA.<br />
Nilsson, H., (1990). Pcrsonal cornrnunication on studded<br />
tyrcs. Nivis Tyrc Inc. Gislavcd, Swcdcn.<br />
Nordstrcim, (1991). Pcrsonal communicillion on tyre<br />
characteristics, ABS, and vehicle dynarnics. VTI,<br />
Linkocping, Swcdcn.<br />
OECD (1990). Behavioural udaptations to changes in the<br />
rof,d transport system. Organisation for Economic<br />
Coopcrrtion and Dcvelopmcnt, Rold Transport Rc*<br />
scarch. Paris. IRRD No 824028.<br />
Pricz. A.. Pctit, C.. Gucz.itrt'|, 8.. Boulommier. L..<br />
Dittmar. A., Dslhomme. A.. Vcrnet-Maury. E.. Pailhous.<br />
E., Forct-Bruno, J.Y., Tarricre, C., ( 199 I ). How<br />
About thc Avcragc Drivcr in a Critical Situation'l Can<br />
Hc Rcally Bc Hclped by Primrry Safcty Improvements?<br />
To bc publishcd in proceedings of the l3th<br />
ESV Conference. Paris, Novernber, 1991. Paper no.9ls7-o-07.<br />
Robinson, 8.J., & Riley, 8.S., (1989). Braking and<br />
Slability Pcrformancc of Cars Fittcd with Various<br />
Types of Anti-Lock Braking Systcfirs. Procecdings<br />
$p.836-846) on the lzth ESV Conference, Gciteborg,<br />
Swcdcn. May 29 - Junc I, 1989.<br />
Rompe, K., Schindler, A., Wallrich, M., (1987). Advantrges<br />
of an Anti-Wheel Lock Syslem (ABS) for the<br />
Average Driver in Driving Situations. Proceedings<br />
$p.aa7-44$ on the I lth ESV Conl'crcnce, Washington,<br />
D.C., May l2-15, 1987.<br />
,.i<br />
1<br />
,<br />
iiir<br />
'E
13th lnternetlonal Technlcal Conference on Exqerlmental Satety Vehlcles<br />
S chlcsselman, J.J., ( I 982). Case-Control S tudies. Oxford<br />
University Press.<br />
Strandberg, L., (19't.2), Mathematical Description of<br />
Vehicle Motion in a Doublc Lane Change Mtlnocuvre.<br />
Chapter 8.7 in VTI Rcpon 9. (In Swedish).<br />
Shandberg, L., (1978). Lateral Stability of Road Tank'<br />
ers. VTI Report l38A (ref. to Volume II, pp. Dl8'<br />
Dzr).<br />
Strandberg, L., Tengstrand, G., Lanshamrnar, H., (1982).<br />
Accident Hazards of Rear Wheel Steered Vchicles. In<br />
G. Johannsen & J.E. Rijnsdorp (eds.),IFAC Analysis,<br />
Design and Evaluation of Man-Machine Systcms.<br />
Pergamon Press, Oxford and New York, 1983.<br />
Strandberg, L., (1989). Skidding Accidents and their<br />
Avoidance with Different Cars. Proceedings (pp. 825-<br />
828) on the lZth ESV Conference, Gdtcborg, Sweden,<br />
May 29 - June l, 1989. Also in VTI Reprint 158'<br />
Strandberg, ( l99l). Case-Control Studies for Asscssment<br />
of Accident Risks in Drivers and Vehiclcs (in Swed-<br />
s7-o.10<br />
Simulation as a Design Aid<br />
E. Girardot, P. Tardivon<br />
PSA Peugeot-Citroen<br />
Introduction<br />
<strong>The</strong> improvement of automotive vehicle road performance<br />
and the manufacturers' concern to optimize<br />
handling charactcristics by adapting thcm to the driver's<br />
capabilities as well as today's road environment, has led<br />
PSA to develop cffcctive research and study methods<br />
used as a preliminary modelling tool in the design office'<br />
This tool must be capable of being adjusted nonempiri'<br />
cally to take account of the numerous porameters which<br />
govern the dynamic response of an automOtive vehicle'<br />
<strong>The</strong> method chosen by PSA brings together thc usc of<br />
open-loop numerical simulation and track testing, associ'<br />
ated with results analysis enabling both objective (variations<br />
curves) and subjective (reprcscntation of vehiclc<br />
behaviour using synthesized images) judgements.<br />
Numerical Simulation<br />
Numerical simulation consists of using a mathematic<br />
modcl to rcpresent the dynamic behaviour of a vchicle.<br />
PSA has several type$ of model at its disposal. Thc<br />
mathematic model used as an example in this papcr has<br />
been produced by dcfining:<br />
. <strong>The</strong> kinetics of a systcm formed from 5 rigid solids<br />
- chassis<br />
- 4 wheels<br />
- engine (reduced to its flywheel) and a material<br />
point: the steering rack location.<br />
. <strong>The</strong> kinetics define thc steering and suspension<br />
systems (wheel plane orientation, induced effecls,<br />
etc)<br />
ish: Besttrnning av olycksrisker hos trafikant och<br />
fordon). VTI Note TF 50-20 (to appear as VTI Repon<br />
367).<br />
Stdttrup-Hanscn, E., Ahlbom, A., Axelson, O., Hogstedt,<br />
C., Juul Jensen, U., Olscn, J., ( 1990). Negittivc<br />
Results-no effect or information? Arbctc och Hiilsa<br />
1990:17, National Institute of Occupational Health,<br />
Solna, Sweden.<br />
Wilde, G.J.S., (1988). Risk Homcostasis <strong>The</strong>ory and<br />
Traffic Accidents: Propositions, deduction and Discussion<br />
of Dissension in Recent Rcactions. ERGO-<br />
NOMICS, vol.3 l(4), pp.44 l-46t3.<br />
Volvo (1989). Volvo Pocket Guidc 1990 (ln Swedish:<br />
Volvo Fickdata 1990). Volvo Car Corporalion, G0teborg,<br />
Swedcn.<br />
VTI, Swedish Road and Traffic Research Institute<br />
( 1990). Annual Report 1989/90. Linkciping, l990 (rcf.<br />
to pp. l9-21).2<br />
. <strong>The</strong> forces<br />
- suspcnsion efforts<br />
- ground/tyre efforts (from tyre condition pnramcters<br />
such its longitudinal slip, tyrc slip angle, etc.)<br />
- aerodynamic efforts<br />
- engine and braking efforts.<br />
<strong>The</strong> vehicle is characterized by about 600 parameters,<br />
the model is driven by a steering wheel angle, an engine<br />
torque and a brake prcssure. Its responsc forms the<br />
vchicle road behaviour (within a ccrtdn ficld of validity).<br />
<strong>The</strong> use of thcsc numerical tools is justified for<br />
many rcasons. <strong>The</strong>y cnahle:<br />
. thc study of a vehiclc which does not yct physically<br />
exist<br />
. pllrametric studies:<br />
quick<br />
- with perfcclly repeatable outside conditions<br />
r a better undcrstanding of the physical phenomena<br />
(notably due to the availability of any required<br />
variable)<br />
. thc rcplacement of actual tests when thesc are<br />
difficult to undcrtake (particularly whcn they are<br />
dangerous) or difficult to interpret.<br />
However, these numerical tools requirc validation for<br />
them to be considered as true vehicle behaviour in a<br />
rcliablc fashion. A test and measutement programr)c on<br />
real vehicles must be carried out to prcciscly define the<br />
model's field of validity of which linritation is known<br />
(particularly due to the stationary functional description<br />
of thc lyrc).
Track Testing (Reconstructing Trajectories)<br />
<strong>The</strong> measurement of cerlain fundamental dynamic<br />
vehicle parameters is difficult (vehiclc trajectory,<br />
chassis, tyre slip angle). PSA has dcveloped a software<br />
programme to reconstruct trajectories fronr simple<br />
mcasurcments takcn on thc vchicle:<br />
' Lincar accelerations at a point according to the three<br />
body axes (refcrcnce)<br />
. Chassis and angle rates (gyroscopic unit)<br />
. Vchiclc spccd (Correvit system)<br />
This software programme cnables access to:<br />
. Chassis condition variables as well as their derivatives<br />
. Normal and tangential acceleration as well as the<br />
trajectory curve radius.<br />
Results Presentation Tool<br />
Apart from the presence of diffcrent varirbles resulting<br />
from the numerical simulation and track tests in the<br />
form of groups of curve.s, the analysis of which gives<br />
rise to a considerable workload, and so PSA has<br />
equipped itself with an animated vehicle movement<br />
scqucnce reprcsentation system.<br />
This is achievcd using a synthesizcd image generator<br />
(G I l0 k SOGITEC) animating 5 bodies (the chassis plus<br />
the four wheels) from their co-ordinates relltive to a<br />
fixcd rcfcrcnce framc. Thc image calculation is carricd<br />
out in real time at a frequency of 25H2.<br />
This typc o[ presentation is a grcat hclp in the work of<br />
result analysis by enabling a subjective visual allpreciation<br />
of the overall vehicle evolution and lhus heing a<br />
complement to the objective judgements made using<br />
curves,<br />
<strong>The</strong> different possibilities linked to synthesized image<br />
generation such as:<br />
. the ability of thc observcr to be positioned anywhcrc<br />
in rclation to thc vehicle<br />
- fixed observer<br />
- observer linked to vehicle movement<br />
- observer at the driving controls<br />
- zoom<br />
the replacement of a solid by a linked trihedron to<br />
demonstratc angular movcmcnt.<br />
. multiplication of the elements to be observed by<br />
using a constant (body angles, wheel angles..).<br />
. slow motion, forward/rewind projection.<br />
. replays<br />
leaving the researcher complete freedom to focus in on<br />
a particular point.<br />
Reconstructing an Accident (Leaving the<br />
Road on a Left-Hand Bend)<br />
In association with other manufacturcrs and the relevant<br />
authorities, P.S.A. is working towards improving<br />
vehicle safety. Notably in the area of primary safety, the<br />
Section 3: Technlcal Sessions<br />
numerical simulation and analysis tools described can<br />
lead to a betlcr understanding of the sequence of events<br />
and the mcchanisrn of an accidcnt.<br />
<strong>The</strong> type of accident sclcctcd (leaving the road on a<br />
bcnd) represents l3% o[ scrious road accidcrtts. Thc one<br />
studied is described as "low dynumics" as the vehicle<br />
spccd on entcring the bcnd was wcll bclow thc maxinrum<br />
possible speed for this type of bend.<br />
Accident Description and Reconstrurtion<br />
<strong>The</strong> police report cnablcs the various phases of the<br />
accident to bc rcconstruclcd:<br />
. A top range car on a 3-lane main road mounted the<br />
verge on the righl-hand sidc of the road in a lefthand<br />
bend.<br />
' <strong>The</strong> vchiclc travelled a distance of 76 metres with<br />
the right-hand wheels al r rnaxinrunr of 1.6 nrctres<br />
ont0 the vergc.<br />
. Thc vchiclc thcn regilined thc road, travclling about<br />
20 metres bclore leaving skid nrarks over a distance<br />
of 2l metres and crashing into a vehicle coming in<br />
the other direction.<br />
Outer H: 23O m Inner H: 500 m<br />
Figure 1. Accident Reconstruction<br />
This report also informs us of:<br />
. <strong>The</strong> vehicle type.<br />
. Thc approximate vehicle triljectory (trajectory whilst<br />
on the grass rnd whilst in thc finill known braking<br />
phase).<br />
. <strong>The</strong> roird condition during the accident: dry road.<br />
. <strong>The</strong> vehicle's final speed of ahout 60 kph detcrmincd<br />
lrorn the slale of the damuge.<br />
. Thc bcnd curve rudius for the lwo vehicles involved.<br />
Ccrtain datlt rcntain urtkrtrtwn:<br />
. <strong>The</strong> driver's behaviour': steering wheel rngle, braking<br />
prcssurc.<br />
. <strong>The</strong> vehicle's initial speed. l<br />
' <strong>The</strong> vehicle load (according to the photos, a relative-<br />
Iy hcavy loitd institlled towlrrds thc rcrrr).<br />
. Thc itctual road adhcsion conditions (typc of surface<br />
and lbove rll the grrss adhcsion conditions).<br />
From rchlivcly rcalistic hypotheses, it is however<br />
possible to re-crlculatc ccrtirin accidcnt data. <strong>The</strong> calculations<br />
show thitt the vchicle was trilvclling at bctween<br />
95 and ll7 kph whcn it wcnt onto the grass. Thc rnarks<br />
left in the grass lry the vehicle show that thc driver was<br />
not brilking during tlris phasc.<br />
<strong>The</strong> drawing produced by the police enilbles us to<br />
evaluate the trajectory curve radius in the grass.<br />
:i;<br />
+ t<br />
rj<br />
.:<br />
J<br />
:!
13th lntemetlonel Teehnlcal Conference on Experlmentel Sefety vehlcles<br />
<strong>The</strong> 500 metre bend curve radius enables us, knowing<br />
the distance covered in the grass and the maximal distance<br />
from the road to the marks left in the grass, to<br />
determine the vehiclc's curve radius on lcaving thc road:<br />
230 metres.<br />
<strong>The</strong> various speeds and rates of deceleration appeilr on<br />
the Reconstructed Accident diagrirm, Figure 2.<br />
*[illl<br />
Figure 2. Reconstructed Accident Diagram<br />
o0lrlfr ilhldb ir<br />
06.1it M<br />
Simulation Produced<br />
By using thc numerical simulation model, from the<br />
availablc accident data and hypotheses on the driver's<br />
behaviour, we have reconslrucled lhe vehiclc cvolution<br />
up to its return to the road (subject vehicle; XM).<br />
Throughout the simulation, brake pressurc is nil and<br />
resistive engine torque 40 mN corrcsltonding to the<br />
accelerator in its highcst position.<br />
Thc simulalion is carried out in two stilges: Figurc 3.<br />
t -3,glg<br />
r-80kPh<br />
Curye radlu8 : 500 m<br />
Conlrol law8<br />
Slacrlng wharl rngla |rw :<br />
ndlrtlw onglm lorque : -4O mN<br />
V6hicle traloclory<br />
Stoorlng whtsl<br />
rngls<br />
(ln degroeE)<br />
t r 17<br />
Flgure 3. Simulatsd Accldent<br />
E<br />
rl<br />
I<br />
l-/ i<br />
t l t -<br />
o q 2<br />
Zona 2<br />
Vohlcle on th8 load<br />
Zona I<br />
VBhicle righl-hand<br />
tyru6 on gftEE<br />
Vrhlcle lBll.hand<br />
lyraa on roE6<br />
I = 0B<br />
E = 117 kph<br />
18,f<br />
' t (ln *cc)<br />
. <strong>The</strong> vehicle has two whccls on thc road and two<br />
wheels on the grass from t=0s to t=2.31s (at thc cnd<br />
of which time thc 76 nctrcs in lhc grass would have<br />
bccn covcrcd). Thc first stlge starts when the two<br />
right-hand vehicle wheels enter the grass. <strong>The</strong><br />
vehicle speed at ihis point is I 17 kph and it is in a<br />
rectilineflr trrjcctory. Thc driver turns thc stccring<br />
whccl at this point front an initial 0 value to a value<br />
of 18.5 degrces in a lincar nlanllet. taking 0.2s (predetermined<br />
anglc lo cnrblc lhc vchicle to describe in<br />
a steady manner a curvc radius of 230 mctrcs; the<br />
steering wheel angle riltc corrcspottds to an avcragc<br />
value). At the end of this first phasc, thc vchiclc is<br />
travclling at 109 kph and has covered 76 rnelres<br />
(average deceleration 0. lg).<br />
N.B. l'hc low adhesion of the grass has been represented<br />
by tyres, thc characlcristics of which wcrc<br />
notcd on a surfrrcc wilh an adhcsion l'ac-tor o[ 0.3.<br />
'Thc vchiclc has l'our wheels on the road (as frotrr t<br />
= 2.31s). Thc second slilge starts when the vehicle<br />
has rclurncd to the road. Steering wheel angle,<br />
enginc torquc and brakc prcssure have been maintaincd<br />
consrilnl, Il is nolcd that this stilge ends wilh<br />
the vchicle spinning nose to tail.<br />
I nterpretation<br />
This reconstruction docs not faitht'ully rcproduce the<br />
accidcnt, [rut abovc all, lrighlighls the influence of the<br />
lack of adhcsion continuity when thc right-hand whccls<br />
pass lrom the road to the grilss. This lack of continuity<br />
in reality ciluses tho drivcr to losc control of the vehicle<br />
which goes into a nosc to tail spin.<br />
Thc curvcs drawn on the figures 4 to'l illustrfltc the<br />
following phenoma:<br />
. <strong>The</strong> discontinuity of liansversal effort on the two<br />
vchiclc right-hand wheels ill th0 momcnl of thc<br />
changc of adhcsion (Figure 4 und 5), ls well as thc<br />
low cvolulion ol' transvcrsll effort on the lcft-harrd<br />
whccls ill lhc sarnc tirrrc (Figurc 6 lnd 7).<br />
. Thc cl'l'cct ol' irnhllitrtcc ort thc trajcctory which<br />
shr wri;<br />
- a shup increase in yawing spccd (Figurc fJ),<br />
- evolution in timc of thc attitude angle which<br />
charactcrizcs thc start of a nose to tail spin (Figure<br />
e).<br />
Compared wilh thc acturl accidcnt, the tnajor differenccs<br />
arc probably:<br />
. lhc hws o[ control applied by the driver (irnpossible<br />
to determine aftcr thc cvcnt)<br />
. the road prolilc (probrblc hcight variation between<br />
rord and vcrgc)<br />
However, hlving takcn thc sirnplest possible hypotheses<br />
for the sirnulation, wc hrvc oblaincd it movcrllcnt<br />
which pcrfcctly rcproduccs thc general t-eatures of the<br />
accidcnl bul nol ncccssarilv lhe exact values of actual<br />
movcillcllts.
F (N}<br />
Figure 4. Ground/Tyre Transversal Effort<br />
(Front Right Whoel)<br />
F (N)<br />
Figure 5. Ground/Tyre Transversal Effort<br />
(Rear Right Wheel)<br />
Tlm. {s}<br />
Tlmo (s)<br />
It can therefore be shown that the lack of continuity of<br />
adhesion bctwccn thc rofld surftcc and thc vcrge cun be<br />
thc causc of a loss of control in a bcnd and this simulation<br />
can be used as the point of departure flor lhe study<br />
of suitablc counter-mcrsurcs.<br />
Conclusion<br />
This presentation has shown, using an application<br />
based on a true case, the results thilt can be obtained by<br />
linking numerical simulation and animation wirh rhc aim<br />
of representing overall vehicle behaviour in a synthesized<br />
manner. Direct observation, in rcal lime, ol' the<br />
vehicle's movement on its trajectory, as well as thc<br />
Sectlon 3: Technica, Sessions<br />
Figure 6. Ground/Tyre Transversal Effort<br />
(Front Left Wheel)<br />
to00<br />
500<br />
25(}<br />
o<br />
-250<br />
-500<br />
-750<br />
F (N}<br />
F {NI<br />
Figure 7. Ground/Tyre Transversal Effort<br />
(Rear Lett Wheel)<br />
s<br />
Tlne (rl<br />
!t<br />
ii<br />
ii !<br />
ii li<br />
i i i!<br />
! ! ii<br />
"Lii- fri<br />
'tt<br />
ji<br />
4 Tlme (s)<br />
accompanying timing dingrnm, provides very useful dtta<br />
explaining the physical phcnonrena.<br />
Bcyond lhc pr-cscnt application of linking vehicle<br />
engine, braking and slcering wilh anirnation, the<br />
introduction of lhc driver in lhe control loop is a way of<br />
further advancing aulomobile vchicle hehaviour analysis<br />
method.<br />
Reference<br />
l. From uccidcntology lnnlysis to thc intelligent<br />
vehicle. I3th ESV Document. Reference 9l-S4-Wl-5.<br />
M. Colinot (PSA) Lcchncr (INRETS) Francc.<br />
829
13th Internetlonel Technlcal Conference on Experlmentel Sefety Vehlcles<br />
7E<br />
25<br />
o 1 2<br />
Flgure 8. Yaw Rate (in Degrees)<br />
-25<br />
Time (r) Tlme (s)<br />
o 1 2 3<br />
Figure L Vehicle Body Slip Angle (in Degrees)<br />
s7-o-tl<br />
Analysis of Accidents in Right Turns Using a Fuzzy Logic<br />
Simulation Model<br />
Hiroshi Ueno, Kiyoshi Ochiai<br />
Nissan Motor Co.. Ltd.<br />
Abstract<br />
<strong>The</strong> objective of this research was to develop and<br />
confirm the validity of a simulation modcl incorporating<br />
fuzzy logic that could be used in analyzing the mechanism<br />
involved in the occurrence of accidents in right<br />
turns. This model is applicable to accidents occurring at<br />
intcrsections in which a vehicle making a right turn<br />
collides with an oncoming vehicle traveling straight<br />
ahead. Such accidents can be traced to driver error<br />
stemming from ambiguous recognition and judgmcnt.<br />
<strong>The</strong> model is capable of analyzing separately and<br />
quantitatively each factor involvcd in the mechanism<br />
causing such accidents. It can be also used to evaluate<br />
the risk involved in the execution of right turns. It was<br />
noted that older drivcrs tcnd to undcrcstimatc the spccd<br />
of oncoming cars. Right turn simulations were conducted<br />
with the model reflected this recognition chffactcristic.<br />
<strong>The</strong> results of the simulations revealed that for older<br />
drivcrs thc time allowance for executing a right turn was<br />
shorter by a maximum of l.0 second in comparison with<br />
younger drivers. In addition, evaluations were also madc<br />
for oncoming cars and motorcycles and for differcnccs<br />
in the perception of oncoming vehiclc speeds and thc<br />
perception of distance under daytime and nighttime<br />
driving conditions.<br />
Introduction<br />
<strong>The</strong> opcration of a motor vehicle entails a repetitive<br />
proce$s of rccognition and judgrnent on the part of the<br />
driver with respect to the condition of the vehicle and<br />
that of the surrounding traffic environmcnt. Thcsc acts of<br />
recognition and judgment contain various ambiguities<br />
that can becorrte the cause of an accident in all too many<br />
instanccs.<br />
In developing prcvcntive safcty systcms, which are<br />
classified under the ciltegory of active safety, it is<br />
essential to understand the mechanism bchind the occurrence<br />
of accidents due to human error in recognizing or<br />
judging a situation. Such understanding provides the<br />
basis for devising safety system concepts which will be<br />
most effective in helping drivers to avoid crrors that lcad<br />
to accidents. Anol.her crucial aspect of this development<br />
work is to establish methocls that milke it possible to<br />
predict the improvcment in sal'ety that can be achieved<br />
through the implementation of a newly developed safely<br />
device or technology.<br />
Thc aim of thc prcsent work was to develop and confirm<br />
the validity of a sinulation modcl thal could be<br />
used in makirrg quilntitiltive analyses of the factors at<br />
work in the occurrence of accidents in right turns (left<br />
turns in thc U.S. and most European countrics). Such<br />
accidents scem to be caused by ambiguities in recognition<br />
and judgntcnt on the part of the driver of thc turning<br />
vehicle, even though the person is awirre of the presence<br />
of an oncoming vehiclc that is travcling straight ahcad.
To accomplish this aim, a comprehensive simulation<br />
model incorporatin g [uzzy logic has been developed that<br />
takes into account the entire right turn process, including<br />
recognition, judgment and execution of driving operations.<br />
Analysis of Right Turns<br />
In ordcr to develop the fuzzy logic simulation model,<br />
it was necessary to analyze the driver behavior that the<br />
model is intendcd to simulate. This was accomplished by<br />
analyzing video tapc recordings of approximately 400<br />
right turns cxccuted at actual intersections. In addition,<br />
approximately 100 right turns were executed at interscctions<br />
without traffic signals by a vehiclc equipped<br />
with various measurement instruments. <strong>The</strong> vchicle behavior<br />
data thus collected were also used in analyzing<br />
right turns.<br />
Video Tape Analysis<br />
Whether a turning vehicle stopped or not showed a<br />
$tronger correlation with the time headway, including the<br />
information on the speed of the oncoming vehicle, than<br />
with the distance from the center of the intersection t
l3th lnternatlonal Technlcal tronference on Experimentel Sefety Vehlcles<br />
Construction of Model<br />
As indicatcd by the task analysis results in the<br />
preceding section, the judgment and operational tasks of<br />
right turns with and without a stop were divided into six<br />
and four phases, respectively. <strong>The</strong> first three phases of<br />
both typcs of right turns flre identical. Thus, the tirsks<br />
performcd by thc driver in cxecuting a right turn consist<br />
of seven phascs in total.<br />
A submodel has been prepared that corresponds to<br />
each individual phase. This was necessiuy because the<br />
information inputs needed to make judgments and perform<br />
driving operations in each phase differ, as do the<br />
outputs (i.e., driver judgment and behavior) of each<br />
phase and the rules used in deriving those outputs. <strong>The</strong><br />
fuzzy logic simulation model for analyzing right turns<br />
consists of seven submodels, as shown in Figure 4,<br />
including three judgment models, which recognize the<br />
status of oncoming vehiclcs and dctcrmine the next<br />
action by the driver of the turning vehiclc, and four<br />
types of right turn behavior models.<br />
Flgure 4. Conliguration of Right Turn Simulation Model<br />
Right Turn Judgment Model<br />
One of the major features of a tuzzy model is that it<br />
is capablc o[ simulating the ambiguous nature of human<br />
rccognition, judgment and operational behavior. Moreover,<br />
it can also be used to perform quantitalivc cvaluations<br />
of the characteristics of these human ilctions.<br />
As an example of the ilpplication of the model, we<br />
will considcr a situation in which a right turn judgment<br />
is made while a vehicle is stopped at an intersection<br />
waiting to turn right. This example will illustrato thc<br />
major feature of a fuzzy model.<br />
Concept of Right Turn Judgment Model :<br />
While the vehiclc is stoppcd at an intersection waiting<br />
to turn right, it is assumed that the driver makes a<br />
prcliminary right turn judgment based on the perceived<br />
spccd of and distance between two oncoming vehicles.<br />
At thc moment when the preceding oncoming vehicle<br />
pa$ses through thc ccntcr of thc intersection, a final right<br />
turn judgment is made on thc basis of the perceived<br />
832<br />
speed of and distancc from thc centcr of the intersection<br />
to the second oncorning vehiclc, i.e., thc ohjcct of the<br />
drivcr's judgment.<br />
Thc object of thc drivcr's judgmcnt shifts to the next<br />
oncoming car at thc point wherc the drivcr judgcs that it<br />
is completely impossible to execute a right turn in front<br />
of the first oncoming car.<br />
Construction of Right'l'urn Judgment Model<br />
lnputs. Inputs includc thc spccd of the oncoming<br />
vehiclc that is thc objcct of thc drivcr's judgment and its<br />
distancc from thc ccnlcr of thc intcrscction.<br />
Outputs. It is assumed that driving operrrtion judgmcnts<br />
arc madc undcr a situittion of competition between<br />
subjcctive feelings of safcty and risk. Accordingly,<br />
judgments that a right turn is possihle or inrpossible are<br />
outpul as a 'Judgmcnt<br />
levcl," rcpresenting a ratio of the<br />
driver's conflicting feelings about the possibility of<br />
executing a right turn.<br />
When either of thc judgment levels showed a value<br />
other lhun 100%. it indicrted an rnrbiguous situation in<br />
which a definitc righl turrr judgmcnt could not bc nradc.<br />
In rerl-world driving. il is ussumcd that thcrc is a<br />
certain threshold ilt work in thc dclcrminltion of drivcr<br />
judgments in such situations. This thrcshold valuc lbr<br />
making such judgrnetrts is assurned to viuy depending on<br />
a variety of factors, such as the personality ancl psychological<br />
stfltc of thc drivcr and the environmental circumstflnces<br />
lt the time.<br />
Membershist J'unctions. Thc degree of ambiguity and<br />
resolution of human pcrccplion of distancc and spccd<br />
correspond respectively to the width of the membership<br />
functions and their number of divisions. Accordingly,<br />
experiments were conducted to obtain birsic informrrtion<br />
on the accuracy of human judgment with respect to<br />
distance and speed.<br />
Rules. Drivers posses knowlcdgc bascd on lcarncd<br />
expcrience that enablcs thcm Lo judgc and cxccutc the<br />
degree of response that is suitablc for a ccrhin levcl of<br />
input. In thc fur,zy logic sirnulation modcl, this<br />
knowledge has been expressed in production rules having<br />
an IF-THEN format.<br />
Tuning of mrmbershilt funetions and rules. <strong>The</strong> analyscs<br />
of lhc vidco tapc rccordings ol right turns indicatcd<br />
that all vehicles turning right stopped rt the intersection<br />
before turning when the time headway to iln oncorning<br />
vchiclc was shortsr than thrcc scconds. Whcn thc timc<br />
headway was longer than six seconds, all vehicles turned<br />
right without stopping. <strong>The</strong> input and output membership<br />
functions and rules were tuned and optimized to simulate<br />
such patterns.<br />
Simulation Resu/Is<br />
<strong>The</strong> simulation faithfully reproduced the results of the<br />
analyses of the video tape recordings of right turns.<br />
Figure 5 shows the simulation results for the relationship<br />
between right turn judgments and thc position and speed
of oncoming vehicles. <strong>The</strong> step-like lines in the figure<br />
indicate the critical lines for right turn judgments with<br />
respect to the threshold values of the right turn judgment<br />
levels. Above this line a right turn is judgcd to be<br />
possible while below the line it is judged to bc impossible.<br />
<strong>The</strong> upper and lower strflight lines indicate time<br />
hcadways of six and three seconds, respectively, for the<br />
oncomins vehicles.<br />
90<br />
o<br />
Eao<br />
P70<br />
Eeo<br />
o<br />
Euo<br />
.9<br />
840<br />
6-<br />
30<br />
Bioht tum<br />
po66lts 1 000/6<br />
t Riliruirpossiblg<br />
0%<br />
Right tum<br />
Dosshle 50%<br />
t Riom ru*<br />
iill9cBbb 50oA<br />
Right tutr<br />
possibls 0%<br />
o<br />
Rioht tum<br />
impossiblo 100%<br />
Figure 5. Reletionship Between Judgments Level<br />
Threshold and Critical Line in Right Turn Judgment<br />
When the threshold value for judging that a right turn<br />
is possiblc is low, the right turn involves a high dcgrce<br />
of risk because there is only a short interval between thc<br />
completion of lhe turn and the anival of the oncoming<br />
vehicle at the centcr of thc intersection. Conversely,<br />
whcn the threshold value is high, thc right turn involves<br />
little risk because there is a long interval from the<br />
completion of the right turn until the oncoming vehicle<br />
rcaches the center of the intersection.<br />
Evaluation of Risk in Right Turns<br />
Present Silualion for Right Turn Acridents<br />
Traffic accident data in the U.S. show that thc percentage<br />
of left turn accidents (right turn in this paper)<br />
among all accidents involving drivers ovcr 60 years of<br />
age is approximately double the corresponding figure for<br />
younger drivers. Accident analysis results in Japan indicate<br />
that right turn accidents involving an oncoming<br />
motorcycle represent 71Vo of all right turn accidcnts.<br />
Approximately 209o of all right turn accidents occurred<br />
even through the driver of the turning vchiclc had<br />
chccked for oncoming traffic and judged that a right turn<br />
was possible.<br />
Concept Underlying Evaluation of Risk<br />
Right turn accidents occur in a "conflict zone,"<br />
representing the space traversed by an oncoming vehicle<br />
as it passes through an interscction. Accordingly, the<br />
index used in evaluating thc degree of risk in right turns<br />
in this investigation was thc time allowance from the<br />
moment thc rcar end of the turning vehiclc clearcd thc<br />
conflict zone until the oncomilrs vchicle reached the<br />
zone.<br />
$ectlon 3: Technlcal Sess/ans<br />
A misjudgmcnt that an oncoming vehicle is farther<br />
away than its actual position corrcsponds to an overall<br />
shift in fuzzy set of thc posilion toward thc nciu sidc.<br />
Since the oncoming vehicle reaches thc intcrscctiorr in<br />
less time than expected, the time allowancc is reduccd,<br />
resulting in greater risk. Similarly, a misjudgrnent thet an<br />
oncoming vehicle is traveling rnore slowly than its actual<br />
speed corresponds to an overall shift in fuzzy sct of the<br />
speed toward the high specd sidc. Thc time allowancc is<br />
thus reduced, resulting in a higher degree of risk.<br />
Conscquently, thc model can provide quantitative estimates<br />
of thc dcgrcc o[ risk in right turns and of the<br />
contribution of cach flrctor involved.<br />
Evslualion Infux for rRist in Right Turns<br />
Collision zone. A simulation conducted with lhe right<br />
turn model with a $top, one of the seven submodcls,<br />
showed that it took the turning vchicle a maximum of<br />
3.2 seconds to pass through the conflict zone. Consequently,<br />
if the time hcadway of the oncoming vehicle<br />
.hat was the object of the driver's judgrnent was less<br />
than 3.2 seconds at lhe point thc right turn judgmcnl was<br />
milde, a right turn accidcnt would occur unless the<br />
oncoming vehicle decelerated. This was defined as the<br />
collision zone.<br />
Dun,qer zone and safery zone,It is reported that a time<br />
allowancc of at least two seconds is generally necessflry<br />
for vehicle maneuvers under ordinary traffic conditions.<br />
Whcn following another vehicle on the freeway, drivers<br />
gcncrrlly allow a time headway of around 1.5 seconds on<br />
avcrcgc. It is assumed that a tirne allowance of at least<br />
1..5 seconds is also necessary lor cxccuting right turns.<br />
In view of these figures, a danger zone was detined<br />
here as an intcrval of lcss thtn 4.7 scconds in terms of<br />
the time from the moment thc driver dccidcs to turn right<br />
and begins to executc thc turn until thc oncoming vehicle<br />
reaches the center of the intcrscction. This intcrval<br />
includcs thc nraxinrum right turn execution time of 3.2<br />
seconds plus I.5 seconds as the minimum value of the<br />
time allowance.<br />
When the interval from thc complction of thc right<br />
turn judgment until the oncoming vehicle reaches the<br />
center of thc intcrsection is longcr than 4.7 scconds,<br />
there is morc lhan amplc timc to cxccutc a right turn<br />
sal'ely. This region was defined rs tlrc sal'cty zone in this<br />
work.<br />
Simulation Results for Evaluation of Risk<br />
Effert of Difft:rtnt Ontoming Vthicle Speeds on tht:<br />
Evaluatiott of Risk itt Right Turns<br />
Otttorning vt:hicIt s1tet:d recognition thuracteristics,<br />
Experiments were conducled to examine the accuracy of<br />
human judgment with respect to the speed of oncoming<br />
vehicles traveling straight ahead. It was notcd that in a<br />
spccd rangc ol'30 to (r0 kn/h, the speed of onconring<br />
vehiclcs was recognized accurately irrcspcctive of the<br />
'i<br />
j<br />
:<br />
r:i<br />
'fl<br />
.
'l3th lntemetlonal Technlcal Conference on Experlmental Safety Vehlcles<br />
vehicle spced. <strong>The</strong> results of nn experiment involving<br />
high oncoming vchicle speeds of more than 70 km/h<br />
showed that the degree of ambiguity in the subjects'<br />
perception of oncoming vehicle speeds increased with<br />
increasing vchiclc spced.<br />
A simulation was carried out to determine what effect<br />
the tendency for greater ambiguity to occur in speed<br />
judgments in the high speed range would have on the<br />
degree of risk in right turns.<br />
Simulation results. Figure 6 shows the critical line for<br />
right turn judgments as a function of the position and<br />
specd of oncoming vehicles in a speed range of 30 to<br />
100 km/h. <strong>The</strong> threshold values of the judgmcnt lcvcls in<br />
this case were 5070 for and 5070 against the possibility<br />
of executing a right turn.<br />
Figure 6. Crltlcal Line lor Right Turn Judgments When<br />
Oncoming Vehicle Speed is Extended to High'Speed<br />
Region<br />
In an oncoming vehicle speed range of 30 lo 50 km/h,<br />
the avcrage time allowance was I.l seconds and the<br />
shortest time allowance was 0.6 second. In an oncoming<br />
vehicle speed range of 7-5 to 100 km/h, the avcragc time<br />
allowance was 0.76 sccond and the shortest timc allowance<br />
was 0.23 second. Compared with the low to medium<br />
specd range, the average time allowance was 0.34<br />
second $horter and the shortest time allowance was<br />
reduced by more than 607o.<br />
<strong>The</strong>se results suggest that the time allowance with<br />
respect to the collision zone is somewhere in the range<br />
of oncoming vehicle speeds ordinarily observed at intersections.<br />
However, the time allowance is reduced as thc<br />
oncoming vehicle speed increascs. When oncoming<br />
vehicles approach interscctions at exceptionally high<br />
speeds, there is a much greater possibility of an accident<br />
occurring.<br />
Effect of Differences Between DaytimelNighttime<br />
Percepilon of Oncoming Vehitlt Distances on lhe<br />
Evaluation of Risk in Right Turns<br />
Characteristits of daytime/nighttime perception of<br />
distance. <strong>The</strong> results of an experiment concerning thc<br />
pcrception of distance to objects indicatcd that distance<br />
judgmcnts at night were around 20 to -50 7o less accurate<br />
than during the daytime. A simulation was carried out to<br />
examine what effect this increase in ambiguity with<br />
834<br />
120<br />
o<br />
o<br />
5 1oo<br />
><br />
o<br />
E<br />
'E 80<br />
a<br />
c<br />
o 6 0<br />
o<br />
E<br />
,H oo<br />
o<br />
L<br />
20<br />
respect to the perception of distancc to oncoming<br />
vchicles would have on the degree of risk in right turns.<br />
Sintulatittn resrlr.s. Figurc 7 shows the critical lines f'or<br />
right turn judgments during thc daylime and nighttime as<br />
a function of thc specd and position of oncoming<br />
vehicles. <strong>The</strong> thrcshold valucs of the right turn judgment<br />
levels were 50To tor and -507o against the possibility of<br />
executing a right turn.<br />
@<br />
E o<br />
o<br />
.E Eooc<br />
o<br />
E<br />
E qo<br />
.L<br />
o Daytime r Nighttime<br />
Figure 7. Comparison ol Critical Lines ol Right Turn<br />
Judgments During Daytime and Nighttime According to<br />
Differences in Perception of Oncoming Vehicle Speed<br />
<strong>The</strong> results indicate that daytime and nighttime right<br />
turn judgments diffcrcd in approximately 40% of all thc<br />
regions included in thc simulation. In the areas whcrc the<br />
judgments differed, thc timc allowance ilt night was<br />
shorter by an avcragc of 0.tt9 second and a maxirnum o[<br />
1.55 seconds. Compared with the shortesl lintc allowance<br />
of 0.34 second during the daytimc, the shortest time<br />
allowance at night wils an extremely small 0.01 second,<br />
which meant thcrc was virtually no leewlry nt all. This<br />
results suggest lhcrc is a strong possibility thal right<br />
turns in nighttirne driving may involve a higher degree<br />
of risk than during the daytime.<br />
Evaluation of Risk in Right Turn Behavior of Older<br />
Drivers<br />
Jurlgment of speed hy older drivers. According to a<br />
study done hy B. Hills et al., older drivers tend to<br />
underestimate the spccd of oncoming vehicles by as<br />
much as lt km/h in comparison with thc pcrception of<br />
vehicle speed by youngcr rlrivcrs in general. This poses<br />
a greater degree of risk in right turns beciluse oncoming<br />
vehicles approach thc inl0rscction laster than older<br />
drivers expect. A simul;tliort wa.s carried out to svilluflte<br />
how rnuch this tendency on thc part of older drivers to<br />
underestirnate vehicle speeds would lhe degree<br />
of risk in right turns.<br />
Simulation results. Figure I shows the critical lines for<br />
right turn judgmcnts by older and younger drivcrs as a<br />
function of the position ilnd spccd of oncoming vehicles.<br />
<strong>The</strong> threshold values of the right turn judgment levels<br />
were 507o for and 5070 flgainst thc possibility of executing<br />
a right turn.
80<br />
@<br />
E70<br />
o<br />
P60<br />
E<br />
8so E<br />
o<br />
Elo<br />
E<br />
.Fo<br />
830<br />
L<br />
20<br />
32sec Collision zonr:<br />
Figure 8. Comparison of Critical Lines of Right Turn<br />
Judgments Between Younger and Older Drivers<br />
According to Dlfference in Perceptlon of Oncoming<br />
Vehicle Speed<br />
Judgments made by younger drivers that a right turn<br />
was possible showed somewhat of a margin with respect<br />
to the collision zone. However, in some cases, the older<br />
drivers judged that a right turn was possiblc when the<br />
time headway to the oncoming car was closc to the colli'<br />
sion zone limit of 3.2 seconds. This suggcstcd that older<br />
drivcrs would face a greatcr possibility of bcing involved<br />
in a right turn accident than younger drivers.<br />
This possibility was also seen in quantitative terms.<br />
<strong>The</strong> critical line for right turn judgments by the older<br />
drivcrs showed an ilvcrage time allowancc of 0.39<br />
second, which was ntuch shorter and only around 36Vo of<br />
the 1.08 second time allowance secn tor the younger<br />
drivers.<br />
In approximately 80% of the cflses simulated, the<br />
judgments of thc older drivers differcd from those of lhe<br />
younEer drivers. In the cases where differcnt judgments<br />
were made, the timc allowance for the older drivers was<br />
shortcr by an average of 0.85 second and a maximum of<br />
1.0 second. Thcsc figures confirmcd quantitatively that<br />
older drivers faced a higher degrcc of risk in right turns<br />
than thcir younger countcrparts.<br />
Evaluation of Risk in Right Turns Involving Oncoming<br />
Molorcycles<br />
Acceptable time headv,uy for motorcycles, A study<br />
done by Nagayama et al. examincd the acceptahlc tine<br />
hcadway of oncoming cars and motorcyclcs.<br />
<strong>The</strong>y tound that the avcragc critical time of lhe<br />
acceptable headway for cars and ntotorcycles was 2.9<br />
and 2.-5 seconds, respcctively. <strong>The</strong>y also rcported that no<br />
significant dilference was obscrved between cars and<br />
motorcycles with respect to the perccption of speed and<br />
disLtnce.<br />
Based on these results, it was assumed that psychological<br />
factors rather than pcrccptional elements had a<br />
largcr effect on diffcrcnces in right turn judgments<br />
betwcen oncoming motorcycles and cars. This diflference<br />
corrcsponded to the change in judgmcnt rulcs in the<br />
fuzzy logic simulation model.<br />
Secllon 3: Technical Sessions<br />
Simulation results.Figure 9 shows thc critical lincs for<br />
right turn judgment in the clsc of oncorning cars ancl<br />
motorcycles as I function of ltrc ltosilion and specd o[<br />
thc oncoming vchicles. Thc lhrcshokl vitlucs of thc right<br />
turn judgment lcvcls were 50t/,, for itnd 50% against the<br />
po.ssibility of cxecuting a right turn.<br />
80<br />
o<br />
E70<br />
o<br />
.9 oo<br />
E R<br />
Es0<br />
E<br />
.E +o<br />
^o<br />
- 3 0<br />
Spe6d of oncoming v6hicl€<br />
Figure L Comparison ol Critical Lines of Right Turn<br />
Judgments for Oncoming Car and Motorcycle<br />
<strong>The</strong> results for cars show that there wils some time<br />
allowancc with rcspcct lo lhc collision zonc. Howevcr.<br />
thc results for motorcycles indicittc that even in lhe<br />
collision zonc judgnrcnts wete still nrirdc lhal a right lurn<br />
was possiblc. This result suEgcsts thal the possibility of<br />
an accident occurring would bc higlrcr whcn the oncoming<br />
vchiclc was il nrolotcycle rather lhan il cilr.<br />
This possihility was also bornc out in quantitative<br />
terms. <strong>The</strong> critical line for right turn judgmcnts when the<br />
oncoming vehicles were rllolorcycles showcd tn average<br />
timc irllowance of 0.38 sccrlrtd as opposed to l.{)l'l sccond<br />
when the oncoming vehicles wcrc cilrs.<br />
In rpproxirnifiely SZEI o[ the cases, differcnt riSht turn<br />
judgments werc made between oncorrting tnotorcyclcs<br />
and oncorning cars. In cascs where diffcrcnt judgncnts<br />
wcrc rnade, thc tirnc allowance for ntotttrcyclcs was<br />
shorter by an averagc of 0.85 second lnd a ntaxirnunr of<br />
1.0 second.<br />
Conclusion and Future Outlook<br />
This simulation ntodcl citn rcprclduce with excclttional<br />
fidelity the real-world bclrlvior displayed by drivcrs and<br />
vchicles in right lurns. Sitttulation rcsulls confirnlcd the<br />
effcctivencss ol this fuz.zy logic lttodel in conducling<br />
qualitutive evlluations of thc flmbiEuous nalurc of hutnln<br />
rccogn it iorr. judgrncnt atrd drivin g operlliotrs.<br />
Thc modcl incorporillos tlrc rcsults of exlcnsivc studies<br />
of various huntan recognition characterislic.s, Thal body<br />
of knowlctlgc sr.rpport$ quilntitative anllyses of thc<br />
factors causing right turn accidcnts due to errors of<br />
recognition, judgment or vchicle opcration on the pilrt of<br />
the driver of thc turning vchicle. Such anllyscs ile<br />
carried out using thc contribution of each factor'<br />
<strong>The</strong> samc proccdure as lhitt followed in devclolling the<br />
sinrulation ntodcl prcsented ltcrc can be used to creale<br />
835
13th lnternatlonal Technlcal Conference on Experimental Safety Vehicles<br />
similar models for analyzing other accident patterns. <strong>The</strong><br />
knowledge and know-how gained through the development<br />
of this modcl should make it possible to explain<br />
different accident mechanisms according to cach factor<br />
involvcd.<br />
By analyzing various accident mechanisms according<br />
to each of the diffcrcnt factors involved and storing the<br />
results in a databasc, it should be possible to construct a<br />
system for assessing the improvcmcnt in stl'cty thrt<br />
might be obtaincd through thc introduction of a new<br />
device or technology. Such an assessment systcm would<br />
be a valuable tool in designing the most cffcctive<br />
preventive safety systems, in itudying and determining<br />
thc optimum system specifications and in evaluating lnd<br />
prcdicting the improvement in safety that could be<br />
achieved by implcntcrrting thc sy$tcm.<br />
References<br />
I. B. Hills, "Vision, visibility, and perception in<br />
driving," Pcrception, 1980, volurne 9.<br />
2. Y. Nagayama, et al., "Spced<br />
Judgmcnt ol'Oncoming<br />
Motorcycles," Procccdings of thc Inlernational<br />
Motorcycle Safety Conterence, 955-971, Washington.<br />
DC. 1980.
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