DELIVERABLE 2.8 - urban track

DELIVERABLE 2.8 

D0208_STIB_M24.doc 

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URBAN TRACK Issued: August 13, 2008 

Quality checked and approved by project co-ordinator André Van Leuven 

Related Milestone 2.1 

CONTRACT N° 031312 

PROJECT N° FP6-31312 

ACRONYM URBAN TRACK 

TITLE Urban Rail Transport 

PROJECT START DATE September 1, 2006 

DURATION 48 months 

Subproject 2 Cost effective track maintenance, renewal & refurbishment methods 

Work Package 2.3 Preventive maintenance of embedded tram tracks 

Rail wear in curves and special trackwork for trams 

Written by André Marqueteeken STIB 

André Van Leuven D2S 

Fritz Kopf FCP 

Date of issue of this report August 13, 2008 

PROJECT CO-ORDINATOR Dynamics, Structures & Systems International D2S BE 

PARTNERS Société des Transports Intercommunaux de Bruxelles STIB BE 

Alstom Transport Systems ALSTOM FR 

Bremen Strassenbahn AG BSAG DE 

Composite Damping Materials CDM BE 

Die Ingenieurswerkstatt DI DE 

Institut für Agrar- und Stadtökologische Projekte an 

der Humboldt 

ASP DE 

Project funded by the 

European Community under 

the 

SIXTH FRAMEWORK 

PROGRAMME 

PRIORITY 6 

Sustainable development, 

Tecnologia e Investigacion Ferriaria INECO-TIFSA ES 

Institut National de Recherche sur les Transports & 

leur Sécurité 

INRETS FR 

Institut National des Sciences Appliquées de Lyon INSA-CNRS FR 

Ferrocarriles Andaluces FA-DGT ES 

Alfa Products & Technologies APT BE 

Autre Porte Technique Global GLOBAL PH 

Politecnico di Milano POLIMI IT 

Régie Autonome des Transports Parisiens RATP FR 

Studiengesellschaft für Unterirdische Verkehrsanlagen STUVA DE 

Stellenbosch University SU ZA 

Transport for London LONDON 

TRAMS 

UK 

Ferrocarril Metropolita de Barcelona TMB ES 

Transport Technology Consult Karlsruhe TTK DE 

Université Catholique de Louvain UCL BE 

Universiteit Hasselt UHASSELT BE 

global change & ecosystems International Association of Public Transport UITP BE 

Union of European Railway Industries UNIFE BE 

Verkehrsbetriebe Karlsruhe VBK DE 

Fritsch Chiari & Partner FCP AT 

Metro de Madrid MDM ES


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T A B L E O F C O N T E N T S 

0. Executive summary................................................................................................................................................. 4 

0.1. Objective of the deliverable .......................................................................................................................... 4 

0.2. Strategy used and/or a description of the methods (techniques) used with the justification 

thereof................................................................................................................................................................ 4 

0.3. Background info available and the innovative elements which were developed............................ 4 

0.4. Problems encountered ................................................................................................................................... 4 

0.5. Partners involved and their contribution .................................................................................................. 4 

0.6. Conclusions ...................................................................................................................................................... 5 

0.7. Relation with the other deliverables (input/output/timing) ............................................................... 5 

1. Introduction............................................................................................................................................................... 6 

2. Build-up welding and related issues................................................................................................................... 7 

2.1. General .............................................................................................................................................................. 7 

2.1.1. Problem description.............................................................................................................................. 7 

2.1.2. Maintenance measures ......................................................................................................................... 8 

2.1.3. Ancillary conditions for build-up welding...................................................................................... 9 

Rail with a tensile strength of up to 700 N/mm²..................................................................................... 9 

Rail with a tensile strength of up to 900 N/mm² (and above).............................................................. 9 

Rail from special material (manganese steel): .......................................................................................... 9 

Remark: Rail of lower quality is easier to « re-vamp » !......................................................................... 9 

2.2. Brussels (STIB)............................................................................................................................................... 10 

Pre-emptive build-up welding for tram rail ........................................................................................... 10 

Lateral widening........................................................................................................................................... 11 

Pre-emptive build-up welding................................................................................................................... 11 

Grinding.......................................................................................................................................................... 12 

2.3. Bremen (BSAG).............................................................................................................................................. 13 

2.4. Saarbahn.......................................................................................................................................................... 15 

Rail profiles of the following quality........................................................................................................ 15 

No pre-emptive build-up welding before installation.......................................................................... 15 

Lifetime of build-up welding..................................................................................................................... 15 

2.5. Augsburg........................................................................................................................................................ 16 


Build-up welding will be carried out as in Saarbrücken...................................................................... 16 

2.6. Karlsruhe (VBK)............................................................................................................................................ 17 


Build-up welding will be carried out according to the local conditions as in Saarbrücken......... 17 

2.7. Vienna.............................................................................................................................................................. 18 

Rails.................................................................................................................................................................. 18 

Build-up welding.......................................................................................................................................... 18 

Test of different welding methods............................................................................................................ 19 

Grinding.......................................................................................................................................................... 19 

2.8. Frankfurt......................................................................................................................................................... 20


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2.9. New developments....................................................................................................................................... 21 

2.10. Conclusions .................................................................................................................................................... 22 

2.10.1. Conclusion about the practice at STIB............................................................................................. 22 

2.10.2. General conclusion about track maintenance................................................................................ 22 

2.10.3. Conclusion for this task...................................................................................................................... 22 

3. The Viennese curve................................................................................................................................................ 23 

3.1. Introduction.................................................................................................................................................... 23 

3.2. Basis of ATM – curve, comparison of kinematics and dynamics....................................................... 25 

The Viennese Curve: .................................................................................................................................... 30 

3.3. Implementation............................................................................................................................................. 33 

3.4. Measurements................................................................................................................................................ 36 

3.5. Evaluation of the Life Cycle Costs of the new geometry ..................................................................... 40 

3.6. Conclusions for the viennese curve .......................................................................................................... 43 

4. Conclusions for this task....................................................................................................................................... 44

0. EXECUTIVE SUMMARY 

0.1. OBJECTIVE OF THE DELIVERABLE 


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The networks of tramway operators in the European city centres comprise many short radius curves. The 

high lateral forces of the vehicles cause the rails to wear quickly. Build-up welding, the most widely used 

method to combat this wear, was developed some 30 years ago. This deliverable thus discusses the 

various techniques that are currently available as alternatives for the technique of build-up welding. In 

addition, this deliverable also discusses the Viennese Curve, a new curve geometry, aimed a reducing the 

wheel rail interaction forces which results in lower wear. 

0.2. STRATEGY USED AND/OR A DESCRIPTION OF THE METHODS (TECHNIQUES) USED 

WITH THE JUSTIFICATION THEREOF 

The various partners in this WP brought their knowledge to the table. Operators from outside the 

consortium were contacted to present their method. A meeting with operators from inside and outside 

the consortium, as well as representatives from the rail and welding industry were invited to comment 

on the various solutions. In addition, the theoretical background and practical experiences with the 

Viennese curve were studied. This was achieved through contacts with Dr. Hasslinger, the inventor, and 

through a literature study on the subject. 

0.3. BACKGROUND INFO AVAILABLE AND THE INNOVATIVE ELEMENTS WHICH WERE 

DEVELOPED 

Although new elements, such as the use of head hardened rails, were explored, they were not found to be 

an alternative to the build-up welding at their present state of development. The Viennese curve is 

already applied in Austria in main line and in the Viennese subway. It has not yet been applied to 

tramway. It is an alternative to reduce curve wear by specific track design. 

0.4. PROBLEMS ENCOUNTERED 

- 

0.5. PARTNERS INVOLVED AND THEIR CONTRIBUTION 

TTK in cooperation with STIB prepared the basic document on rail welding. TTK used its contacts with 

other operators from inside (RATP, BSAG, VBK) and outside the consortium to get their input and their 

presence at the workshop on rail welding. D2S arranged the participation of rail manufacturers. FCP 

obtained the information on the Viennese curve from operator Wiener Linien.

0.6. CONCLUSIONS 


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Flange lubrication is beneficial in reducing wear on wheels and rails. 

Vignol rails of Q900 are recommended in non-embedded curves (they have a lower wear rate) where 

exchanging the rail is easy. 

Grooved rails of Q700 are recommended on embedded curves (it is possible to build them up 8 times 

and to bend them without special difficulties) where exchanging the rail is difficult and expensive). 

This restriction is possible with some special heat treatment on site. The first treatment can be done 

in the workshop before installation in order to reduce squeal noise in the curve, or it can be done after 

the first wear cycle (up to 16 mm wear is accepted in practice). After treatment, the rails of Q700 have 

the same hardness as Q900 rails. Grooved rails of Q900 are recommended on tangent track. 

New developments proposed by the rail manufacturers such a use of head rail in curves with a 

specific wear restoration procedure are still in prototype development phase. 

Specific track designs, such as the Viennese curve, are promising for wear reduction but not 

applicable for embedded tram applications. 

No further research or validation is required concerning this topic. 

0.7. RELATION WITH THE OTHER DELIVERABLES (INPUT/OUTPUT/TIMING) 

-

1. INTRODUCTION 


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The networks of tramway operators in the European city centres comprises many short radius curves. 

The high lateral forces of the vehicles cause the rails to wear quickly. The most widely used method to 

combat this wear was developed some 30 years ago. The technique consists of cleaning the worn section 

to bear steel so that a new layer can be welded in to restore the rail to its as new profile. With the older 

mild steel rails this technique can be applied up to 10 times before rail replacement becomes necessary. 

As the cost of rail replacement of embedded rail is several times higher than that of normal grade 

separated track, it is important that the rails remain is service as long as possible. This deliverable 

discusses the various techniques that are currently available as alternatives for the technique of build-up 

welding. 

The following solutions are considered to increase the life of rails in curves: 

� gauge widening; 

� wider grooved rails (Ph37a); 

� lubrication; 

� head hardened rail; 

� build-up welding; 

� grinding; 

� exchange of rail.


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2. BUILD-UP WELDING AND RELATED ISSUES 

2.1. GENERAL 

2.1.1. Problem description 

Figure 2.1 

Severe wear of rail in curves. 

Ancillary conditions for build-up welding dependent on the material. 

E.g. pre-heating for steel with high tensile strength. 

Narrow curves most often are situated in an unfavourable road/surface environment, so a change of 

rail is difficult and cost-intensive. 

Problem of change related to the wear of wheel/rail. 

Manganese steel/wear of wheel rim in Croydon (figure 2.1).

2.1.2. Maintenance measures 

Figure 2.2 


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Widening of the rail geometry in narrow curves. 

Use of rail with larger groove width (Ph 37a) where possible in the track’s environment (e.g. turn 

backs). 

Lubrication (lubricant or water) in narrow curves (figure 2.2). 

Use of rail with hardened head. 

Build-up welding (rail head). 

Grinding. 

Exchange of rail.


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2.1.3. Ancillary conditions for build-up welding 

Rail with a tensile strength of up to 700 N/mm² 

no problems, material safe to work with. 

Rail with a tensile strength of up to 900 N/mm² (and above) 

Pre-heating is necessary for the first ignition of the arc (to 400°C), this temperature needs to be 

maintained throughout; this poses a difficulty due to the conditions prevailing on the construction 

site (weather, tram/car traffic, measuring equipment measuring surface only etc.) . 

Rail from special material (manganese steel): 

only to be welded with matched filler metals; the parts worked with have to be cooled (e.g. dry ice). 

Remark: Rail of lower quality is easier to « re-vamp » !

2.2. BRUSSELS (STIB) 


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Pre-emptive build-up welding for tram rail 

For rail with radii < 250 m (up to min. 17m). 

Grooved rail of the 700+ Vanadium (685-835 N/mm 2 ) quality. 

Increasing the hardness up to approximatively �500 HB (comparable to the 900A-rail), which 

considerably reduces the lateral wear of rail in curves. 

Initial welding process in the workshop (even before instalment). 

Build-up welding is possible up to 8 times (on site). 

Steel quality Materials for build-up welding (on site) : 

C 0.20 - 0.30 % 0.07 

Mn 1.20 – 1.50 % 7 

Si 0.20 – 0.30 % 0.9 

P

Figure 2.3 

Figure 2.4 

Lateral widening 


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Lateral widening of the dimensions to approx. 9 mm width and 12 mm depth. 

For grooved rail at the railhead for the outer rail in the curve (figure 2.3 left). 

At the outside edge for the inner rail (figure 2.3 right). 

Preliminary stage for the pre-emptive build-up for rail with difficult wear profile. 

Pre-emptive build-up welding 

Realisation in four steps with two automatic welding heads. 

Hardness when building up: 185 HB. 

Hardness after a period of use: 450 to 500 HB.

Figure 2.5 

Grinding 


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After build-up and full cooling of the rail, the weld seam is ground. 

Recreation of the original rail geometry with a �1 mm tolerance.

2.3. BREMEN (BSAG) 


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The practice at BSAG is similar to Brussels with the exception that they do not perform the pre-emptive 

build-up welding. BSAG installs the rail as is and welds in the field when necessary. Until about 20 

years ago, BSAG also did pre-emptive build-up welding before bending the rails. This gave problems 

during the bending as the two different metals (bimetal) behaved differently and caused the weld to split 

off from the rail. The welding is now performed by an outside contractor in which BSAG owns 51%. The 

60% of paved track is Ri59 and previously Ri60, all of Q700. The 40% open track is 49E1 (earlier S49) of 

Q900 and before S41 of Q700. 

Another difference is the track design, which prevents wheel from touching the lip of the rail. The lip 

cannot be used for guidance. That means that BSAG only has (lateral) wear on the railhead. The 

introduction of the new low floor trams in 1996 has changed the wear pattern. Before there was only 

wear on the outer rail in curves with a radius below 40 m. Now the wear is distributed with 1/3 on the 

outer rail and 2/3 on the inner rail. On new rails, the inner rail needs treatment first. This is also due to 

the selection of the rail: NP4am (and also Ri60) has a groove of 34 mm, whereas Ri59 has a groove of 

42 mm. The extra 8 mm make that there is less contact with the flange. BSAG designs its tracks to avoid 

flange wear on the back of the wheel. BSAG used to remove up to 9 mm lateral and 7 mm vertical. This 

caused problems when welding again. When the rail wears in the vertical direction, the weld may split 

off. 

BSAG was also experimenting with Q900 rail to avoid welding. Now Q700 grooved rail is used; they still 

see normal wear on the railhead with lateral wear of 6 mm after 12 to 18 months before re-welding. The 

next re-welding then takes place when the wear is 7 mm, i.e. when it is more than the layer added in the 

previous re-welding process. In the next step a wear of then e.g. 8 mm is allowed, then 9 mm etc where 

BSAG allows a maximum gauge widening of 20 mm. 

BSAG also introduced wheel flange lubrication. The second welding now takes place after 2 to 3 years 

with a material of the same quality as Q900. It is normal practice to do the build-up welding 8 times, 

using the same material as Brussels. Rail life this way can be extended to about 15 to even 20 years. 

The main advantage of not welding pre-emptively is the cost of machining the rail. 

Since 1996 all vehicles are equipped with wheel lubrication which has generated a reduction in welding 

costs of 15% with the added benefit that squeal is eliminated.

Figure 2.6 


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Quality checked and approved by project co-ordinator André Van Leuven

2.4. SAARBAHN 

Figure 2.7 

Rail profiles of the following quality 

Ph37a / Ri59N, 700 N/mm². 

S49 900 N/mm². 

No use of head hardened rails. 


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No pre-emptive build-up welding before installation 

Lifetime of build-up welding 

In curves depending on the radii and the allowed speed. 

In tight curves ca. 3-4 years.

2.5. AUGSBURG 

Figure 2.8 



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Ri 60, 700 N/mm² (partly head hardened). 

S 41, 900 N/mm². 

In the future only use of grooved rails with 700 N/mm². 

Bad experience with head hardened rails (welding is very difficult and time consuming). 

Build-up welding will be carried out as in Saarbrücken.

2.6. KARLSRUHE (VBK) 

Figure 2.9 



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S 49 / Ri 59N, 700 and 900 N/mm². 

Use of 900 N/mm² for test purposes in curves. 

Use of grooved larger groove width (Ph 37a) e.g. in turnouts (figure 2.9). 

At small radii there is a tendency towards grooved rails with 700 N/mm². 

Build-up welding will be carried out according to the local conditions as in Saarbrücken.

2.7. VIENNA 

Figure 2.10 

Rails 


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Rails of 700 N/mm² quality, when head hardened 800 N/mm². 

Use of 900 N/mm² for test purposes in curves. 

Build-up welding 

After data verification of rail measure vehicle, and visual inspection. 

4 – 5 welding teams in service every night (0.30 – 5.00 h). 

80-90% of the work carried out by external private companies. 

15 – 20 m for every night (3/4 of the time for welding purposes). 

Depending on the wear the weld metal bead will be applied in several layers.

Figure 2.11 

Figure 2.12 

Test of different welding methods 


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WL is currently testing different welding methods for different rail qualities. 

Verification of the quality on behalf of test examples of welded rails (figure 2.11). 

The results cannot be published yet. 

Depending on the wear, the weld metal bead will be applied in several layers on top of each other. 

Grinding 

Grinding after build-up welding. 

Depending on the radii different space measuring devices (in German: Raumbedarfslehren) will be 

used to grind the profile in the best way (Space for wheel flange in the groove depending on the 

radii). 

Afterwards the profile is compared using a template (figure 2.12).

2.8. FRANKFURT 


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VGF (Frankfurt) operates 300 km of track with a 50/50 split between grooved and vignol rail. The 

introduction in 1995 of the low floor vehicles caused the same problems as in Bremen. VGF uses the 

following tools: 

One lubrication vehicle; 

Stationary lubrication systems (which cause problems during welding); 

Resilient wheels on vehicles operating in the city. 

Since 1988 they use the same welding technique as in Brussels on rails with low carbon content. 

They use Riflex (Electrothermit) of 1700 N/m with Q800 on the top of the rail to combat corrugation and 

ETEKA 5 of 1400 N/m on the side of the rail to combat wear. The problem is the splitting off of the weld 

under the vertical wheel load. The Riflex was ground away and the rails finished with Citorail (= DUR 

300). 

This technique had the following problems: 

The rails are not machined for the pre-emptive welding, but grooves are burned out. Therefore the 

rails have to be carefully cleaned. Otherwise, the welds easily break out of the rail head. 

The material characteristics change during the heating process (e.g. rail welding). This produces a 

surface with inconsistent properties that results in weak spots (20 cm each side of the weld) and 

variations in the rail height. 

The material easily breaks away from the rail head and requires frequent weld repairs and frequent 

grinding after the repairs. 

The method requires a lot of attention and is very costly. 

In 1998 they worked with perlitic vignol rail with Q1100 on the outer rail and Q880 on the inner rail. 

Grooved head hardened rail had to be removed after the welding of the lip which caused the lip to break- 

off. Currently they use Ri59 and Ri60 of Q700. 

The rails are installed as delivered and wear reaches 7 mm after only 6 months. Wear increases both on 

the head and on the lip and reaches 12 to 15 mm after 14 months. They use the same welding material as 

in Bremen. UGF also has flange lubrication installed on 20 vehicles. 

The cost of rail replacement is 1400€ per m; build-up welding 80€ per m and normal rail welding 80€ per 

weld.

2.9. NEW DEVELOPMENTS 


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Corus is fully aware of the importance of the weld restoration coating process as it is significantly more 

cost effective that the renewal of embedded tracks. 

The key requirements of the new system are: 

the use of steels with higher carbon content than grades 700/800 to reduce wear; 

a process for in situ restoration without destroying the surrounding jacket; 

restore the worn face with a more resistant wear coating resulting in a composite rail; 

repeated application of the coating process. 

A new submerged arch welding process was developed that uses a specifically formulated flux, a cored 

arc wire and flux powder. 

Steps of the process: 

1. Light grind cleaning of the worn face; 

2. Preconditioning with a novel “chill removal” treatment in the area to be restored; 

3. Weld deposition of the root pass; 

4. Weld deposition with subsequent passes until the worn portion has been restored; 

5. Deposition of a capping weld bead as a final sacrificial layer; 

6. Grinding to remove the sacrificial layer and to impart the desired gauge corner profile. 

The key to creating the hard weld is the pre-conditioning “chill removal” treatment, which results in: 

a crack free root pass of the weld deposit; 

a hard but tough tempered martensitic microstructure in all passes. 

The removal of the sacrificial last pass leaves a tough wear resistant surface 

A purposely designed welding unit achieved the following: 

10 to 12 m in a 4.5 hour track possession; 

Capability of restoring more than 10 mm; 

Preference to 6 mm wear. 

The process is under still under development and is applied in Sheffield. 

The following problems still need to be addressed: 

The “chill removal” process is difficult to execute on an embedded rail and needs enhancement. 

Currently the experience is limited to only one restoration on a rail. 

The conventional process can be repeated several times. 

The preference is to restore after 6 mm of wear whereas the conventional process can rebuild after up 

to 20 mm of wear and this can be repeated up to 6-8 times. 

The technique is not yet used on a wide scale: prototype evaluation is on going.

2.10. CONCLUSIONS 

2.10.1. Conclusion about the practice at STIB 


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The build-up welding practice at STIB is the current state of the art. The rails quality is Q700 and the 

welding materials are also the same. 

The differences can be summarised as follows: 

STIB is the only one present that is until doing the pre-emptive welding on the new rails in order to 

prevent squeal noise. Other operators do not face this problem since they have vehicles equipped 

with wheel lubricators. 

STIB uses the lip to guide the wheel and thus experiences wheel wear on the lip as well. 

STIB uses rails with a narrower groove. 

2.10.2. General conclusion about track maintenance 

Flange lubrication is beneficial in reducing wear on wheels and rails. 

Vignol rails of Q900 are recommended in non-embedded curves (they have a lower wear rate) where 

exchanging the rail is easy. 

Grooved rails of Q700 are recommended on embedded curves (it is possible to build them up 8 times 

and to bend them without special difficulties) where exchanging the rail is difficult and expensive). 

This restriction is possible with some special heat treatment on site. The first treatment can be done 

in the workshop before installation in order to reduce squeal noise in the curve, or it can be done after 

the first wear cycle (up to 16 mm wear is accepted in practice). After treatment, the rails of Q700 have 

the same hardness as Q900 rails. Grooved rails of Q900 are recommended on tangent track. 

New developments proposed by the rail manufacturers such a use of head rail in curves with a 

specific wear restoration procedure are still in prototype development phase. 

Specific track designs, such as the Viennese curve, are promising for wear reduction but not 

applicable for embedded tram applications. 

2.10.3. Conclusion for this task 

No further research or validation is required concerning this topic.

3. THE VIENNESE CURVE 

3.1. INTRODUCTION 


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From the very beginning of railway engineering the design of the ideal track geometry layout was a key 

problem. Two hundred years ago, with the debut of the steam engine simple geometric and kinematic 

basics were developed which are still valid today. From then to now engineers were busy to develop a 

track alignment that reduces forces in the wheel – rail contact point, minimizes wear of the tracks and the 

wheels and that advances the safety of the passengers. 

A reduction of discontinuities (reduction in the mathematical order) was first proposed by F.R. Helmert 

in 1872 and G. Schramm in 1934, who replaced the straight course of the cant gradient and curvature by 

two curves, thus dividing the element into two. In 1936, A.E. Bloss proposed the simplest possible 

polynomial for a simple part element, which is now increasingly used. As early as 1907, K. Watdrex 

achieved a further reduction of discontinuities with a sinus-shaped curse. These two curves solve the 

problem of discontinuities at the joints in the first. 

Really fundamental investigations were done by Dr. Walter Heindl for the Österreichische Bundesbahnen 

(ÖBB) since 1988. He developed the first homogeneous systems of methods and rules based one pure 

geometry (strip theory), kinematics and physics. The method was mathematically perfect, but seems to 

be unacceptable for use by the railway organisations. 

Hence, a new start was made by Austrian Railways, the Wiener Linien and Dipl.-Ing.Dr.techn. Herbert 

L. Hasslinger a civil and mechanical engineer from Vienna in 1995. A homogeneous system of rules 

covering conventional and modern track alignment designs was created. A new simple method and new 

curves just fulfilling the basic demands were developed. The result is the “Viennese transition curve and 

cant gradient” type HHMP7. It shows the typical “out-swinging” as an effect of “track alignment design 

for the centre of gravity” that was already known by the other researchers, but never constructed in such 

an easy manner. This design feature is protected by international patents, which are jointly owned by 

Wiener Linien and by ÖBB, the Austrian Federal Railways. 

The Wiener Linien operates and enlarges its net already in this modern manner and ÖBB has used the 

transition curve many times in its network. 

A comparative measurement investigation was performed for the verification purposes and for gaining 

practical experience. The conventional geometry of clothoid and constant cant gradient was perfectly 

executed and tested by a measurement train. Afterwards the modern geometry was tamped and tested 

following the same procedure. The first inspection already shows that typical peaks at the connecting 

areas vanished with the new geometry. The comprehensive deterministic and statistic evaluation clearly 

proofs the advantages of centre of gravity alignment design through better running characteristics. 

Therefore, a better track stability can be expected. 

A carriage's centre of gravity is not at the same height as the track alignment, yet contemporary transition 

curves (clothoid, Bloss-curve, Schramm-parabola, co sinusoidal curve, and sinusoidal curve) ignore this 

fact. This explains why additional forces are needed to move the centre of gravity on elevated tracks.

Figure 3.1 


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These forces are channelled into the track and cause increased wear and tear and maintenance costs. This 

also causes the carriage to sway, which reduces passenger comfort. 

In the meantime, the new transition curve has been used in the ÖBB network and in the Viennese 

Underground many times. The first test results were positive and so the Viennese Curve was authorized 

for use in general route design in the revised edition of the route guidelines (B50 - track routing). The 

design of the Viennese Curve now has been authorized in the new routing guidelines of the Austrian 

Railways (ÖBB). These routing guidelines cut down on unnecessary wear and tear and improve 

passenger comfort. The Viennese Curve is easily recognisable in the curvature string because of its 

characteristic amplitudes in the opposite direction of the curvature. 

nolmalised amount of curverture 

Curvature alignment for centre of gravity 

normalised chainage


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3.2. BASIS OF ATM – CURVE, COMPARISON OF KINEMATICS AND DYNAMICS 

Figure 3.2 

The main difference between the standard curve (clothoid) and the Viennese Curve is in the advanced 

line management. The advantages of the modern geometry are obviously. The centre of gravity 

guidance of the vehicle is optimised and has very low and continuous accelerations and low guiding 

forces. The track is continuously defined while its loading is minimal and known. The track alignment 

height is based on the centre of gravity. Due to the smooth ramp, transition low decay rates of the track 

are expected and demonstrated. 

The following picture shows the curve driving powers which affect the track and the vehicle and due the 

passengers. 

Curve Driving Powers at the drive over a curved track 

The transition curves used so far had straight cant gradients. The impact of substantial forces at these 

transitions has resulted in greater rail and wheel wear. Such conventional transitions also reduce the 

passengers’ ride comfort and safety by causing noticeable transverse jerks. In addition, such areas 

frequently develop track geometry defects. 

The Viennese Transition Curve provides for a verifiable reduction of rail wear in curves and for an 

extended life cycle in comparison with a conventional alignment geometry based on clothoid and straight 

cant gradients. Moreover, the new design feature improves the accuracy of track position. The advanced 

track alignment used for the Viennese Transition Curve is the key to maintaining the desired track 

geometry. This in turn will extend the life cycle and reduce life cycle costs. In addition, the constant and 

non-jerking movement of vehicles obtained in curves will greatly improve passengers’ riding comfort 

and safety.


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Quality checked and approved by project co-ordinator André Van Leuven

Figure 3.3 


TIP5-CT-2006-031312 Page 27 of 44 



Differences between the conventionally alignment and the Viennese Curve 

The conventionally alignment (clothoid), considers the vehicle as a mass point moving longitudinally on 

the centre of the track. Superelevation is achieved by rotation in the track plane. The centre of gravity of 

the vehicle lies not on the centre of the track but in a certain height over the track. The Viennese Curve 

allows leading the vehicle in a way, that the curve driving powers directly affect the centre of gravity. 

Discontinuity in the vehicle movement, forces, peaks and jerks are going to be minimised with this new 

alignment. 

The smooth drive over, and the lower forces at the beginning and the end of the transition spiral cause 

fewer maintenance interventions and therefore reduced costs.

Figure 3.4 


TIP5-CT-2006-031312 Page 28 of 44 



LCC (Life Cycle Cost) analyses have very clearly shown the positive effect on life cycle costs and 

maintenance work. This optimum course taken by the forces involved will result in a reduction of both 

rail and wheel wear. 

The track serves as guidance for the moving vehicle and is responsible for its dynamics. For the 

investigation of kinematics, at least a general point in the cross section of the vehicle has to be observed, 

not a point in the track plane, which is from a mathematics view a singular plane. For the dynamics, 

Newton’s and Euler’s laws have to be taken into consideration. For both, the centre of gravity is the 

decisive point. Therefore, track alignment design has to be performed for this centre. The track should 

provide continuous variations for at least velocities and accelerations and preferably also jerks 

everywhere within the vehicle. 

On the other hand, the track is the support structure for internal forces (in the rails) and external forces 

caused by the moving vehicles. The continuous welded rails have to be bent and kept in the required 

shape. This is only possible with a special continuous variation of cant gradient. In a ramp, the railroad 

track is always stressed. 

The normalized pattern and derivatives look like: 

Normalized constant cant gradient and curvature and derivatives 

The kinematics induced by a constant cant gradient without rounded connections are typical. There is a 

step in the elevation angles of the cant gradient at the boundaries. The sway (roll) angular velocity is 

discontinuous, therefore the sway (roll) angular acceleration is infinite, which causes also the non- 

compensated transverse acceleration in the centre of gravity to be infinite. The sway (roll) angular jerk is 

infinite, which causes also the non-compensated transverse jerk in the centre of gravity to be infinite. If 

only the outer rail is elevated also vertical acceleration and jerk are infinite. Rounded connections are 

needed to remove these singularities, which elongate the cant gradient in an undefined manner. With 

circular rounded connections, only accelerations are limited, but not the jerks. 

Another important aspect is to consider the rail(s) as (a) bended beam(s). For the bending of the rail, in 

that context a simple Bernoulli - Euler – model suffices.

Figure 3.5 


TIP5-CT-2006-031312 Page 29 of 44 



It has to be applied biaxial, in the stiff up direction of the web and in the weak transverse direction of the 

foot 

For a conventional geometry, the ideal position of the continuous welded rails in plain lines lead in the 

maximum to the following discontinuities: 

Transverse direction: Small steps in the curvature (connections of two circular curves without 

transition curve) or kinks in the curvature (at a clothoid). 

Up direction: Steps in the angles (at a constant cant gradient) equalling kinks in the position. 

As can be detected immediately, up direction are two orders worse than transverse direction! 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

VA71 

UIC60 

UIC54E 

S49 

-80 -60 -40 -20 0 20 40 60 80 

Typical rail cross sections 

Taking into consideration the formulas of basic bending theory, for the nowadays used cant gradient can 

be derived: 

All nowadays used cant gradients have discontinuities at the ends, if one order does not match that of 

the neighbouring rough track alignment design element (straight all derivatives = 0, circle only zero th 

derivative (cant) � 0 ). 

The discontinuity is forced by a continuous distribution of the loadings due to the rail fastenings 

analogous formula of Zimmermann (Hetényi). 

Assuming a special shape of the loading distribution, which generates the wanted geometry of the 

rail in the cant gradient, either the amplitude of the force or the length of the rounded connection can 

be calculated. 

The prescribed geometry is not realized there!


TIP5-CT-2006-031312 Page 30 of 44 



Either huge force amplitudes or long areas with geometry other than the prescribed one are obtained. 

Especially, for constant cant gradients the following results are estimated: 

Sharp kinks at the ends of constant cant gradients are impossible for continuous welded rails. 

There are always rounded connections, which elongate the constant cant gradient. 

Steep constant cant gradients have either a great length of the rounded connections (>> 10 m) or high 

stress in the railroad track. 

Therefore, rapid decay of the track alignment geometry starting from the kinks of the straight ramp. 

Steep and short constant cant gradients are never straight but everywhere bended. 

Curvature and cant in the rounded connections are no longer proportional. 

The Viennese Curve: 

The Viennese transition curve and cant gradient and its similar products have a very smooth connection 

to the neighbouring elements and are based on a high order function. They all fulfil the following 

requirements: 

Acceleration and jerk are continuous and smooth, not only in the track centre line, but also 

everywhere within the guided vehicle. 

In the cant gradient, the continuous welded rails are not forced to yield the prescribed geometry. The 

shape is kept with minimal forces obeying bending theory. 

Track alignment design is performed for a certain height (the medium height of centres of mass of the 

vehicles), not for the singular track centre line. Therefore, guiding forces are kept small. 

The Viennese curve has the simplest mathematical description for the fulfilment of all these demands: 

Low forces (external from the vehicle and internal from the track). 

Less maintenance (high potential for durability). 

The following graphs show the basic functions and their derivates in comparison with the well-known 

transition curves presently used.

Figure 3.6 

Figure 3.7 

Bezogene Überhöhung 

1 

0,9 

0,8 

0,7 

0,6 

0,5 

0,4 

0,3 

0,2 

0,1 

0 


TIP5-CT-2006-031312 Page 31 of 44 



Alle Überhöhungsrampen - Lage 

0 0,2 0,4 0,6 0,8 1 

All cant gradients - position 

Bezogene Winkel 

2,5 

2 

1,5 

1 

0,5 

0 

-0,5 

Bezogener Weg 

Alle Überhöhungsrampen - W inkel 

0 0,2 0,4 0,6 0,8 1 

All cant gradients – angles 

Be zoge ne r W e g 

Linear ramp 

Bloss ramp 

COS (Japanese) ramp 

Helmert (Schramm) ramp 

Watorek ramp 

SIN ramp 

Herbert's HT ramp 

Viennese type HHMP7 

© Hasslinger 

Linear ramp 

Helm ert (S chramm ) ramp 

Blos s ram p 

COS (Japanes e) ram p 

W atorek ram p 

SIN ram p 

Herbert's HT ram p 

Viennes e type HHM P7 

© H asslinger

Figure 3.8 

Bezogene Krümmung 

8 

6 

4 

2 

0 

-2 

-4 

-6 

-8 


TIP5-CT-2006-031312 Page 32 of 44 



Alle Überhöhungsrampen - Krümmungen 

0 0,2 0,4 0,6 0,8 1 

All cant gradients - curvatures 

Be zoge ne r W e g 

Linear ramp 

Bloss ram p 

COS (Japanese) ram p 

Helm ert (S chramm ) ramp 

W atorek ram p 

SIN ram p 

Herbert's HT ram p 

Viennese type HHM P7 

© H asslin ger 

The position of the ramp is directly built with the basic function. The first derivative is proportional to 

the rail inclination angle and the angular velocity about roll axis, the second derivative is proportional to 

the angular acceleration about roll axis and the bending moment about transverse axis in the rail, the 

third derivative is proportional to the angular jerk about roll axis and the shear force in upright direction. 

The smooth junction with the constant functions at each side can be proven. 

To prove the superiority of this advanced curve design an ideal reproduction of conventional curves 

(clothoid) with straight cant gradients was built and negotiated with a track recording train during 

nightly downtimes. The track recording train conducted acceleration measurements in a series of 

measuring runs. Then the curves were retamped to introduce the new alignment geometry (Viennese 

Transition Curve and cant gradients) and the measuring runs repeated with the track recording train. 

The following comprehensive deterministic and statistic evaluation clearly shows that vehicle movement 

was improved by the new alignment geometry (see Illustration).

3.3. IMPLEMENTATION 

Figure 3.9 

Figure 3.10 


TIP5-CT-2006-031312 Page 33 of 44 



The first Viennese transition curves and cant gradients were built by ÖBB near the stopping place 

Poehndorf of Western main line track 1 Frankenmarkt – Ederbauer of Austrian Railways with a Plasser & 

Theurer Stopfexpress of Bahnbau Wels in summer 2001. 

Situation in Poehndorf: Stopfexpress Frankenmarkt - Ederbauer 

Plasser & Theurer Win-ALC and begin of Viennese curve 

The two Viennese curves lead to a radius of 420 m and cant of 152 mm, one from the Viennese side, the 

other from the Salzburg side. They substitute conventional clothoid transition curves with constant cant 

gradients. The engine drivers confirm an excellent comfort negotiating the new transition curves.

Figure 3.11 

Figure 3.12 

Figure 3.13 


TIP5-CT-2006-031312 Page 34 of 44 



Viennese transition curves eastern side to Vienna (right track) and western side (left track) 

Differenzrichtungsswinkel [gon] 

0,1 

0,08 

0,06 

0,04 

0,02 

-0,04 

-0,06 

-0,08 

Richtungswinkeldifferenz Wiener Bogen - Klothoide 

0 

276070 

-0,02 

276110 276150 276190 276230 276270 276310 

Station s [m] 

pHHMP7-pKloth 

© Hasslinger 

Differenzquerlagen [m] 

0,03 

0,02 

0,01 

-0,01 

-0,02 

-0,03 

Differenzquerlage Wiener Bogen- Klothoide kubische Integration im optimalen System 

0 

276070 276110 276150 276190 276230 276270 276310 

Differences of angle of direction and track displacements (transverse shift) from the clothoid 

Differenzüberhöhung [mm] 

10 

8 

6 

4 

2 

-4 

-6 

-8 

-10 

Überhöhungsdifferenz Wiener Rampe - gerade Rampe 

0 

276070 

-2 

276110 276150 276190 276230 276270 276310 

Station s [m] 

ABSuMP7-ABSuK 

Differences of cant to constant cant gradient 

© Hasslinger 

A comparison between the conventional and modern track alignment shows the main differences and 

demonstrates the main vantages of the Viennese Curve. 

Stations [m] 

y3HHMP7-yKloth 

The conventional geometry shows, that at the connections the centre of gravity of the vehicle is undefined 

and poor guided. Due the high accelerations of the vehicle causes large guiding forces. The shape of the 

cant gradient is obtained by large forces with high and unknown loadings of the track, which causes 

kinks. 

In opposite the modern track alignment is everywhere well defined and the centre of gravity of the 

vehicle is guided calm. Low accelerations cause low guiding forces. The shape of the cant gradient of the 

© Hasslinger

Figure 3.14 

Figure 3.15 


TIP5-CT-2006-031312 Page 35 of 44 



rail is obtained with al low exact known track stability and is therefore economical efficient Viennese cant 

is the only one realized which fulfils all the demands from the bending theory with known forces to keep 

it in shape. 

The jerks caused by track alignment design are continuous everywhere within the vehicle. 

It has the simplest mathematical description and is optimal suited for track alignment for centre of 

gravity. 

Modern cant gradient Viennese type 

It is the only curve and cant gradient with varying curvature which can be expected to be stable by 

reasons of the theoretical demands. 

Accelerometers at the front axle bearing; at the bottom triaxial + 2 transverse for check of accuracy; 

beneath the roof over the front bogie

3.4. MEASUREMENTS 


TIP5-CT-2006-031312 Page 36 of 44 



The verification of the advantages of modern track alignment design compared to conventional one is 

done by measurement of accelerations at the metro train of Wiener Linien. The main task is to find the 

influence of track alignment design by measurement of the accelerations at the vehicle. The 

measurements were done with extremely sensitive, low frequency, accelerometers (applied sub critical, 

displacement s = F/c = - a/�0², �0 = 2(((f0 characteristic frequency). The first test-measurement with 8 

channels was realized one morning and followed by the main-measurement of the track geometry with 

up to 18 channels in 3 nights during pause of normal operation. The measurement of the whole metro 

net with 20 channels each line was realized twice in two days during normal operation with high 

frequency sensors in up-direction at the axle bearings. 

Accelerometers were mounted on the axle bearings in transverse (low frequency) and vertical (middle 

frequency for ripple) direction, in the middle of the bogies, at the bottom of the vehicle’s body in 

longitudinal, transverse (triaxial) and vertical direction over both bogies and in the middle, at the left and 

right outer walls in vertical direction and beneath the roof in transverse direction approximately over 

both bogies. 

Marker equipment with inductive approach switch for the exact spatial determination of the vehicle’s 

position was used. Therefore, mean values could be taken for different runs at the same position. A 

series of measurement runs were performed at the night both in travelling and in reverse direction and at 

different speeds. 

The procedure for three test-curves at the metro U4 was the following: 

Production of the ideal old conventional geometry with clothoid and constant cant gradient. 

Measurement of accelerations with measurement train. 

Re-tamping to Viennese transition curve and cant gradient. 

Measurement of accelerations with measurement train. 

Evaluation of the actual accelerations relative to the nominal accelerations (maximal 0,654 m/s²). 

Calculations of the dispersions = SQRT(variances) of the mean accelerations within the vehicle’s body 

in [m/s²].

Figure 3.16 


TIP5-CT-2006-031312 Page 37 of 44 



Comparison old and new alignment design track 2 section C travelling direction 

Between Vienna U4 stations Friedensbrücke and Spittelau at track 1 between Friedensbrücke and a 

switch connection and further on between that connection and the begin of tunnel to Spittelau each a 

clothoid with constant cant gradients was substituted by modern Viennese transition curves and cant 

gradients and at the other track 2 for the reverse direction between the switch connection and 

Friedensbrücke the same was done for one transition curve and cant gradient.

Figure 3.17 


TIP5-CT-2006-031312 Page 38 of 44 



Figure 3.17 shows a typical time plot along the clothoid with constant cant gradients before the 

reconstruction and afterwards the Viennese transition curves with Viennese cant gradients, the switch 

connection is in the middle of picture. The investigated transition curves are outmost left and right in the 

picture. 

Comparison old and new alignment design track 1 sections A and B travelling direction


TIP5-CT-2006-031312 Page 39 of 44 



By means of the marker signals, the time plots were recalculated to path plots and the evaluation of the 

vehicle’s relative accelerations related to the track induced accelerations is done for every channel. A 

deterministic and statistic evaluation is performed. The results are for the both directions: 

Table 3.1 Relative accelerations mean bottom of vehicle statistic and deterministic results travelling direction 

Empiric 

dispersions 

1. measurement 

06. August 2001 


13. August 2001 


27. August 2001 

FB-AU track 1 

Region A 

Clothoid with constant cant 

gradient 

0,109 

Viennese curve & cant gradient 

0,074 


0,086 


Region B 


gradient deterministic 

evaluation: Large oscillations 

AU-FB track 2 

Region C 

No measurement 

Undefined intermediate state Clothoid with constant cant 

gradient 

0,153 


deterministic evaluation: 

reproducible 

Table 3.2 Relative accelerations mean bottom of vehicle statistic results reverse direction 

Empiric 

dispersions 


06. August 2001 


13. August 2001 


27. August 2001 


Region A 


gradient 

0,125 


0,090 


0,089 


Region B 


gradient: 

0,171 

Viennese curve & cant 

gradient 

0,124 

AU-FB track 2 

Region C 

No measurement 

Undefined intermediate state Clothoid with constant cant 

gradient 

0,142 


0,153 

Viennese curve & cant 

gradient 

0,132 

Beside the reduction of the dispersions the results of the measurements from the time plot show: 

At the bogie: the differences between the two types of geometry cannot be seen due to the large 

amplitudes; the running characteristics are dominating. 

Much higher accelerations at the roof than at the bottom. 

Vehicle body has smaller non-compensated accelerations on the newly tamped track; it is guided 

calmly. 

When compared to conventional clothoid curves, the vehicles run more deterministic than stochastic 

with much smaller amplitudes on the Viennese transition curves. 

The fluctuation of non-compensated acceleration is evident smaller and the empiric dispersions are 

reduced. 

Is valid independently from the travelling direction.


TIP5-CT-2006-031312 Page 40 of 44 



3.5. EVALUATION OF THE LIFE CYCLE COSTS OF THE NEW GEOMETRY 

Figure 3.18 

For the verification and obtaining of practical experience a comparative measurement investigation was 

performed. The first inspection shows already that typical peaks at the connecting areas vanished with 

the new geometry. The comprehensive deterministic and statistical evaluation clearly proofs the 

advantages of centre of gravity alignment design by means of better running characteristics. This reduces 

the wear and hence the current maintenance cost. 

The lower wear of the tracks and the lower strain of the track superstructure extend the service life in the 

track and the lifecycle of the track superstructure. Hence the lifecycle cost drops. In addition the lower 

wear has a positive impact on the current costs. Previous experiences show, that a reduction of the 

lifecycle costs of up to 15% can be expected. In the following figure the differences in cost of installation 

and maintenance between the conventional alignment and the Viennese Curve are illustrated. Although 

additional expenses due the ATM-curve are expected, the total costs, due the maintenance savings 

because of the new alignment are reduced. 

LyfeCycle Cost model

Figure 3.19 


TIP5-CT-2006-031312 Page 41 of 44 



LCC Model: Results of the ATM – curve 

A few Viennese Curves were already implemented by the Österreichischen Bundesbahnen (Austrian 

railway, see capture …) and monitored over 6 years. It was found, that due the lower forces between 

wheel and track at the beginning and the end of the transition curve, fewer damages are estimated. 

Hence there was no maintenance necessary. In comparison with the conventional alignment, two times 

track packing with adjustment of the track level was necessary during this period. The result of the 

monitoring shows, that the ATM (Advanced Track Alignment) reduces cost through less maintenance 

work and longer lasting stability of the track structure. The additional expenses because of the advanced 

track alignment amortise quite shortly. Figure 3.20 shows the payback periods for the ATM-curve and 

the comparison of design expenses and maintenance savings. The cost savings by means of the ATM 

curve are demonstrated in figure 3.21. It is shown that the Viennese Curve is expected to produce cost 

savings of up to 12%.

Figure 3.20 

Figure 3.21 


TIP5-CT-2006-031312 Page 42 of 44 



Payback period for the ATM-curve. Comparison of design expenses and maintenance savings 

Cost saving by means of the ATM – curve


TIP5-CT-2006-031312 Page 43 of 44 



3.6. CONCLUSIONS FOR THE VIENNESE CURVE 

The Viennese Curve will be implemented in new lines and in the retamping of the sleepers of existing 

ballast tracks of the Wiener Linen (Vienna public transport) and the Österreichischen Bundesbahnen 

(Austrian Railway). For the heavy railway the Viennese Curve is regulated in the internal standard B50 - 

track routing. In metro tracks, the Viennese Curve is installed in several test sections since about three to 

four years. The rail profile, wear, and also the horizontal alignment have been measured periodically 

since the construction, but there is no analysis of the data up to now. For tracks embedded in roads, the 

Viennese Curve usually is not convenient because of the defined cant, which is not compatible with the 

pavement.

4. CONCLUSIONS FOR THIS TASK 


TIP5-CT-2006-031312 Page 44 of 44 



Build-up welding as it is done at STIB is the current state of the art and forms the basis for all other 

measures regarding track maintenance in curves and especially for embedded tracks. This topic does not 

require any further research or validation. 

The Viennese curve so far is only implemented in heavy rail and metro, and has not yet been 

implemented on tramway where tight curves are prevalent. Even Wiener Linien who developed the 

geometry still has to implement it for tramway. The geometry has the potential to reduce wear in curves 

and could be implemented on tracks in their own right of way.

DELIVERABLE 2.8 - urban track

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