Powerpoint

The PAFV test and roadfrictionKym NeaylonPrincipal Research EngineerARRB

Contents• Background – why worry?• British vertical-wheel PSV test• NSW horizontal-bed test• Australian PAFV test• PSV/PAFV relationship with on-site friction• The Wehner Schulze test• Seasonal variation• The Wilson test method• Conclusionswww.arrb.com.au 2

BackgroundFactors contributing to road crashesVehicle2465Driver21 24Source: Adapted from Wilson 20062Road environment•Hz Hz. & Vt. Alignment•Traffic volumes•Conflicting events•Clear zones•Pavement conditionwww.arrb.com.au 3

Pavement ConditionPolished aggregatewww.arrb.com.au 4

Microtexture and Polished Aggregatesg- through a microscopeSource:www.arrb.com.au 5

1950s – British PSV polishing machineSource: Feighan (2006)www.arrb.com.au 6

1950s - Australia‘Sydney's traffic densities have increased considerably’www.arrb.com.au 7

1960s – DMR NSW Horizontal bed machineSource: AS 1141.41 – 1984 (superseded)www.arrb.com.au 8

Then the Australian PAFV test• By mid 1970s – no specific Australian Standard• Most states used British PSV vertical wheel withBritish reference aggregate, grit & tyres• NSW committed to DMR horizontal bed• AS1141-1984, introduced PAFV test, allowed bothvertical wheel and horizontal bed, with Aust.reference aggregate, grit & tyres• PAFV Polishing regimes were specifically designedto give results comparable between the Hz & Vt.Methods, and similar to the British PSVwww.arrb.com.au 9

Changes in PAFV and PSV testsThe PSV test has since changed in some of these:• Coarse abrasive• Water & abrasive feed rates• Polishing time• Reference aggregate• Rubber for friction testingTherefore PSV and PAFV results may now not bedirectly comparablewww.arrb.com.au 10

1995 - Possible relationship betweenPSV (vert. wheel) and PAFV (flat bed)6055PAFV504540PSV v PAFV1:1 line3535 40 45 50 55 60PSVSource: Private correspondencewww.arrb.com.au 11

Relationship with on site friction:The old British PSV test0.70SFC (meansummer valu ue)0.65060 0.600.550.500.450.400.350.30PSV = 65PSV = 60PSV = 55PSV = 50PSV = 450 500 1000 1500 2000Commercial vehicles per lane/daySource: Szakowski and Hosking (1972)www.arrb.com.au 12

Relationship with on site friction:1990s British workBand I - Traffic light controlled intersections,pedestrian/school crossingsBand III - Intersections0.600.55Band I0.600.55Band IIIPredicted MSS SC050 0.500.450.400.35PSV6560555045Predicted MSS SC050 0.500.450.400.35PSV65605550450.300 1000 2000 3000 4000 5000 60000.300 1000 2000 3000 4000 5000 6000Expected traffic (CVD)Expected traffic (CVD)Source: Roe and Hartshorne (1998)www.arrb.com.au 13

Relationship with on site friction:2000s - Wehner Schulze testTest samplesPolishingworkstationFrictionmeasuringworkstationSource: Neaylonwww.arrb.com.au 14

Wehner Schulze - test apparatusPolishingrollersFrictionmeasuringpadswww.arrb.com.au 15

Seasonal VariationMelbourneVictoriaiUK Seasonal variationWestern AustraliaPerthSource: Rogers & Garget (1991) Source: Oliver, Tredrea, Pratt (1988)www.arrb.com.au 16

Wilson 2006accelerated polishing machine, dynamic frictiontester, seasonal variationSource: Wilson 2006www.arrb.com.au 17

Conclusions• The PSV test from 1950s has remained simple• Skid resistance environment has evolved• UK debate. PSV test only a ranking methoddependent on particular stresses generated by thetest itself?• What about stresses found in the field?• Germany, France, UK, Ireland, NZ investigatingalternative tests• Sophistication could include seasonal variation?• Australia needs to be aware of this debatewww.arrb.com.au 18

And finally…………..This is a very difficult problem to master.Will one single test ever accurately rank allaggregates under all conditions?www.arrb.com.au 19

………..the endwww.arrb.com.au 20

The Vehicle.Car tyres early 1900’ssquare, solid rubberSource: http://newspapers.nla.gov.au/ndp/del/homewww.arrb.com.au 21

The vehicle: Car tyres 1934 to 2004www.arrb.com.au 22

Wehner Schulze testFriction Measuring WorkstationPolishing WorkstationPolishing rollersFeet with rubber padsPolycarbonate shieldPolycarbonate shieldSpecimen mounted in mouldQuartz abrasive + watermixing tankRound Table mountedon runnerSource: Dunford 2008www.arrb.com.au 23

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