deliverable d1.4 small prototypes of green tram tracks ... - urban track

D0104_ASP_CDM_M24.doc 

TIP5-CT-2006-031312 Page 1 of 27 

URBAN TRACK Issued: 29/8/2008 

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

DELIVERABLE D1.4 SMALL PROTOTYPES OF GREEN TRAM 

TRACKS FOR LAB TESTS 

Related Milestone M1.2 

CONTRACT N° TIP5-CT-2006-031312 

PROJECT N° FP6-31312 

ACRONYM URBAN TRACK 

TITLE Urban Rail Transport 

PROJECT START DATE September 1, 2006 

DURATION 48 months 

Subproject SP 1 Low Cost Modular New Track Systems & Fast Installation Methods 

Work Package WP 1.2 Technical Developments: Design of Ecological Tracks 

Small Prototypes of Green Tram Tracks for Lab Tests 

Written by Martin Richter, Hendrikje Schreiter, Didrik Thijssen ASP, CDM 

Date of issue of this report 29/8/2008 

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

PARTNERS Société des Transports Intercommunaux de Bruxelles STIB BE 

Alstom Transport Systems ALSTOM FR 

Project funded by the 

European Community under 

the 

SIXTH FRAMEWORK 

PROGRAMME 

PRIORITY 6 

Sustainable development, 

Bremen Strassenbahn AG BSAG DE 

Composite Damping Materials CDM BE 

Die Ingenieurswerkstatt DI DE 

Institut für Agrar- und Stadtökologische Projekte an der 

Humboldt Universität zu Berlin 

ASP DE 

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





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

0. Executive Summary ..........................................................................................................................3 

0.1. Objective of the Deliverable..............................................................................................................3 

0.2. Strategy Used and/or a Description of the Methods (Techniques) Used with the Justification 

Thereof................................................................................................................................................3 

0.3. Background Info Available and the Innovative Elements Which Were Developed .....................3 

0.4. Problems Encountered ......................................................................................................................4 

0.5. Partners Involved and Their Contribution.......................................................................................4 

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

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

2. Description of Prototypes with Sedum Vegetation ......................................................................7 

2.1. Structure of Test Bodies.....................................................................................................................8 

2.1.1 Grass Paver .....................................................................................................................................9 

2.1.2 Substrate..........................................................................................................................................9 

2.1.3 Anti Root Foil..................................................................................................................................9 

2.1.4 Drainage/Base Layer....................................................................................................................10 

2.1.5 Special Absorber ...........................................................................................................................11 

2.2. Prototype 1 (Special Absorber – Drain Concrete)..........................................................................14 

2.3. Prototype 2 (Special Absorber – Rubber Mat) ...............................................................................16 

2.4. Prototype 3 (Grass Paver)................................................................................................................17 

3. Description of Prototypes with Artificial Grass..........................................................................19 

3.1. Artificial grass..................................................................................................................................19 

3.2. Track design.....................................................................................................................................20 

3.3. Artificial green track prototypes.....................................................................................................21 

4. Tests and Action Performed ..........................................................................................................25 

4.1. Pre-cultivation..................................................................................................................................25 

4.2. Fatigue Tests ....................................................................................................................................25 

5. Tests and Action Planned ..............................................................................................................26 

5.1. Noise Measurements at Brussels Test Site .....................................................................................26 

6. Problems Encountered ...................................................................................................................27

0. EXECUTIVE SUMMARY 





0.1. OBJECTIVE OF THE DELIVERABLE 

This deliverable describes prototypes of developed green tram track designs which meet the 

requirements of technical standards and come up with solutions to specific problems. Within 

the Urban Track project a sustainable, low maintenance, improved noise absorbing, well water 

balanced green track with regard to the particular local climate and required technical 

standards (stray current) has to be developed, which allows occasional use of emergency 

vehicles. Track design, materials and plant varieties influence those parameters, thus were 

developed or chosen according to their particular suitability, respectively. 

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

(TECHNIQUES) USED WITH THE JUSTIFICATION THEREOF 

The strategy is to develop a vegetation system and track design, according to the problems and 

requirements of green tram tracks and conducting tests on materials to be considered. Review 

and specific tests on applicable materials for green tram tracks regarding their characteristics to 

our SWP- objectives were done and have influenced the material choice. Certain parameters of 

the developed solutions were further modified and will underlie additional developments 

based on the results gained during further tests and the first practical test at Brussels (SP3). 

0.3. BACKGROUND INFO AVAILABLE AND THE INNOVATIVE ELEMENTS 

WHICH WERE DEVELOPED 

Background info available: 

- Specifications provided by IASP 

- Specifications provided by STIB 

- Specifications provided by CDM 

Innovative elements: 

- low maintenance drivable solution using Sedum. 

- with Sedum pre-cultivated grass paver. 

- using a better noise absorbing material as rail shoulder than conventional concrete or the 

known rubber elements (e.g. from Sedra or Kraiburg).





- preventing excessive weed growth at the connection of the root foils and the sides of the 

track by means of inserting the foil end into the concrete board separating the track from 

the road and into the longitudinal concrete beam in which the rail is embedded. 

- improved quality of last generation artificial grass. 

- limiting maintenance and good drivable solution using artificial grass. 

0.4. PROBLEMS ENCOUNTERED 

IASP 

During the fatigue test the drainage material had to be changed, as both split and gravel were to 

similar in grit size and therefore not compressible enough. This caused loss of time, with the 

effect that firstly only 2 prototypes (version 1) could be tested properly and secondly that this 

test only comprised 4,600 wheel crossings. Consequently not all test questions have been 

answered. 

No suitable grass paver for our pre-cultivation purposes is available on the market. Producers 

are not interested in developing a new design at the moment, because of high costs for a new 

mold. 

Moreover, an industrial bonding of the foil to the sides of the track is needed. It is being tested 

at the moment if a pre-cultivation without fleece was feasible. 

CDM 

It was difficult to simulate the real situation of artificial grass at the test circuit of STUVA. No 

real problems have been encountered. 

0.5. PARTNERS INVOLVED AND THEIR CONTRIBUTION 

CDM basic track design 

design of rail jacket and concrete beam 

ongoing development of combination of artificial and real vegetation 

shared tests (e.g. noise absorption, fatigue test, Brussels test site) 

STIB (WP 3.2) operator of Brussels test site





have specific demands on track design 

STUVA conduct fatigue test 

IASP Development of vegetation system with real plants 

0.6. CONCLUSIONS 

This deliverable provides input to SP1 and SP3, for those applications were green tram tracks 

are planned to be used. 

It also has relations with SP4 because of the life cycle cost calculations that have to be 

performed.

1. INTRODUCTION 





This deliverable describes prototypes of developed green tram track designs which meet the 

requirements of technical standards and come up with solutions to specific problems: Within 

the Urban Track project a sustainable, low maintenance, improved noise absorbing, well water 

balanced green track with regard to the particular local climate and required technical 

standards (stray current) has been developed, which allows occasional use of emergency 

vehicles. Track design, materials, plant and artificial grass varieties influence those parameters. 

They had to be developed or chosen according to their particular suitability. 

To ensure the passage of emergency vehicles the developed green tracks must be able to carry 

the load of these vehicles. Therefore a fatigue test at STUVA was carried out. For the detailed 

description of the test equipment see D2.11 prepeared by STUVA.





2. DESCRIPTION OF PROTOTYPES WITH SEDUM 

VEGETATION 

Three different green tram track prototypes have been developed so far. They are going to be 

tested and optimised during SP 3.2. They represent three track design versions which are going 

to be put into practice in a test zone in Brussels, each. All three of them aim to reduce as much 

reverberant track surface as possible to mitigate noise reflection. These prototypes are built for 

fatigue testing at the test site of the project partner STUVA. The test conditions determine the 

outer dimensions of the test bodies. The three design versions implement an extensive, thin 

layered vegetation system which applies Sedum-moss vegetation. The dimensions of this 

system result from plant needs and low maintenance reasons, since the drought tolerant Sedum 

only needs fertilizer once a year and survives dry periods better than any other plant or weed 

which might start to grow in the track. A more detailed explanation why this vegetation system 

was chosen is given in the last progress report for D1.3 (2007). The single elements are described 

more detailed in this year’s final deliverable D1.3 (2008). The dimensions of the rail parts (rail, 

rubber jacket, concrete foot) are supplied by CDM (see D1.4 from CDM). Design and 

dimensions of the prototypes are shown in the figures below. 

For the test bodies no plants are used since this does not give additional information. 

Steel frame, rail and rail encapsulation of the 6 prototypes were built by CDM and transported 

to STUVA where the prototypes were tested for their fatigue stability. Mr. RIFFEL from 

HEIDELBERGCEMENT installed drain concrete in 2 prototypes at STUVA test site, which had to 

dry for 28 days. IASP did the finish by installing the vegetation system: drainage layer, foil, 

grass paver, Xeroterr I (substrate). 

The 3 versions were repeated twice (6 test bodies), each repetition filled with either gravel or 

split.





2.1. STRUCTURE OF TEST BODIES 

Figure 1: Overview of the vegetation system / track design. Left: special noise absorber as hard 

shoulder, Right: grass paver up to rubber jacket 

Standard structure of the test bodies: 

Drainage layer / 

base layer 

� 19.5 cm 

Anti root foil � 0.5 mm 

� 3 bodies received a split filling (8/16), 

� 3 a gravel filling (8/11); 

� In later tests the two bodies of version 1 received a mixture of mineral 

materials (grit size 0/32) 

� PE 

Grass paver � 5 cm thick 

Area next to rail 

(hard shoulder) 

� Fleece (0.2-0.5 mm) glued to the bottom 

� Filled with 4 cm Xeroterr I (substrate) 

� Consisted either of drain concrete (version 1), rubber absorber 

(version 2) or grass paver (version 3)

2.1.1 Grass Paver 





The top of the prototype consist of grass pavers (System: SCHWAB), which have a thickness of 

51 mm. 

Figure 2: Grass paver, System SCHWAB Figure 3: Grass paver prepared for pre-cultivation by gluing 

fleece to the bottom, to prevent soil from falling 

out during transport 

These pavers are assembled from single elements (size: 580 x 380 x 51 mm). Since the vegetation 

is going to be pre-cultivated in these grass pavers and transported to the installation site 

afterwards, a fleece (approx. 0.2-0.5 mm) needs to seal the bottom part of the grass pavers to 

prevent the substrate from falling out during transport. This fleece is glued to the grass paver 

and is permeable to water. 

2.1.2 Substrate 

The substrate level within the grass paver is 40-45 mm. This ensures plant re-growth in case of 

plant damaged by car tires. The substrate used is going to keep a stable structure so that the 

level filled in the grass paver will be obtained. 

2.1.3 Anti Root Foil 

Below the fleece material, an anti-root foil, made of PE with a thickness of 0.5 mm, is installed. 

To ensure a good drainage during heavy rain the foil is perforated (diameter: ca. 1 mm) every 

running meter. To keep the foil closely connected to the sides it was thought to be incorporated 

into the rubber jacket during production process, 51 mm below the surface, about 30 mm deep 

but could not be realized as such. This fixation is necessary to ensure position stability of the foil 

and to prevent weed growth by restricting the substrate level to 4 cm thickness. 

For the prototypes of version 1 the anti root foil could not be clamped between the concrete 

types as planned, since Mr. RIFFEL from HeidelbergCement predicted problems with the bond





of the concrete otherwise. Therefore it was bent down in a 90° angle along the concrete beam 

and held by the drainage, more or less. 

For the prototypes of version 2 (rubber absorber) the foil was glued to rubber absorber and 

concrete beam by means of Sikaflex (SIKA Deutschland GmbH) (see Figure 1, left side). The 

bonding was not very tight and resulted in bad bonding of the rubber absorber to the concrete. 

During the first fatigue tests the grass paver gave way to the load applied so the rubber 

absorber received the full load of the tyre on one side and came off. 

For the prototypes of version 3 (grass paver) a slot was cut into the rubber jacket, surrounding 

the rail. The foil was pushed into the slot with difficulties and though glued did not clung very 

well. 

2.1.4 Drainage/Base Layer 

For the first fatigue test run the drainage layer of the prototypes was made of gravel with grain 

sizes 8/11 mm (version 1-3) as well as of split (8/16), (version 1-3). A more stable behaviour of 

split compared to gravel was expected, due to its shape. This layer is usually constructed as fine 

plane with a 1% slope towards the middle of the track. 

Figure 4: Split (8/16) Figure 5: Gravel (8/11) 

Since those materials were not stable enough during the test (neither split nor gravel) they were 

replaced by a mixture of mineral materials (0/32) in both prototypes of version 1 (drain 

concrete). This material was far more compressible and therefore was stable enough to carry the 

load of emergency vehicles (wheel load during fatigue test: 3.5 t).

Figure 6: Mineral mixture (0/32) 

2.1.5 Special Absorber 

Drain concrete (TioCem) 





A new material, drain concrete “TiOCem” developed by HeidelbergCement has been tested 

and can be implemented as special absorber. 

Figure 7: Drain concrete (HEIDELBERGCEMENT) 

Figure 8: Conversion of NOx to NO3 - by titanium dioxide and UV-radiation (HEIDELBERGCEMENT)





Drain concrete is an open porous concrete which possesses a good noise absorption, with up to 

5 dB(A) (RIFFEL, HEIDELBERGCEMENT), is drainable, therefore increases evaporation and 

converts NOx to NO3 - by incorporated titanium dioxide. 

Figure 9: Typical composition and quality requirements of drain concrete 

Concrete strength class C 20/25 

Aggregate Fine flint 5/8 mm 1,450 – 1,500 kg/m³ 

Cement CEM I 32,5 R 300 - 350 kg/m³ 

Water (Fresh water) 50 - 55 kg/m³ 

Synthetics dispersion 

20 % of weight (10 % 

solids) 

60 - 70 kg/m³ 

w/c-factor 0.24 – 0.26 (effective) 

Consistency V 1.30 – 1.34 (C1) 

Void content P � 20 Vol.-% 

Compression strenght fck* � 25 N/mm² 

Bending tensile strenght fct* � 3.5 N/mm² 

Splitting tensile strenght fct* � 2.7 N/mm² 

Adhesive tensile strenght fct � 1.5 N/mm 2 

Static modulus of 

elasticity 

�B 

16,000 – 18,000 N/mm²

Porous rubber (CDM 46) 





The CDM porous rubber mat 46 is made of rubber granules of shredded tires which are bonded with a 

polyurethane binder under high pressure. During impedance measurements in the previous year this 

mat showed the best noise absorption of the tested materials (see progress report D1.3). 

Figure 10: Porous rubber mat (CDM 46) 

Figure 11: Typical composition and quality requirements of CDM 46 

Prescription Unit CDM-46 

Material Resin bonded rubber 

Colour black 

Density - ASTM-D297 kg/m³ 990 

Shore hardness -ASTM-D2240 °A 50-60 

Tensile strength – ASTM-F152 MPa > 0.5 

Elongation at break - ISO-37 % > 40 

Compressability at 2.8 MPa – ASTM-F36 % 30-50 

Recovery at 2.8 MPa - ASTM-F36 % > 90 

Compression set 50%/23°C/70h – DIN53572 % < 10





2.2. PROTOTYPE 1 (SPECIAL ABSORBER – DRAIN CONCRETE) 

In Prototype 1a special noise absorbing drain concrete was implemented next to the rubber 

jacket which encapsulates the rail. The drain concrete replaces the upper part of the in Brussels 

usually used concrete beam, surrounding the rubber jacket. The dimensions of the drain 

concrete are 51 mm (thick) x 90 mm (wide). 

Figure 12: Prototype version 1, special noise absorbing and NOx converting TioCem drain concrete 

next to rail





Figure 13: Installation of TioCem drain concrete 

Figure 14: 6 empty test bodies for fatigue test, 

IASP 

Figure 16: Anti root foil (version 2) 

Figure 15: Drainage layer filled in (version 3) 

Figure 17: Fitting of grass paver to test body shape 

(version 3)





Figure 18: Drain concrete prototype, ready for testing 

2.3. PROTOTYPE 2 (SPECIAL ABSORBER – RUBBER MAT) 

Prototype 2 is a variation of Prototype 1. The difference is an additional material (special noise 

absorber) implemented next to the rail on top of the concrete which can be used to drive on. 

This accommodates operators which prefer a firm shoulder next to the rail. For the prototype 

the rubber mat “CDM 46” is used. This material can be prefabricated and installed with lower 

efforts than the slightly more noise absorbing drain asphalt. The dimensions of the rubber mat 

are 51 mm (thick) x 90 mm (wide). 

Figure 19: Prototype version 2, noise absorbing porous rubber mat (CDM 46) as hard shoulder





For the prototypes in version 2 a slot was cut into the rubber jacket, surrounding the rail. The 

foil was pushed into the slot with difficulties. The 0.5 mm anti root foil was glued between 

absorber and concrete by means of Sikaflex glue. But as already predicted the bonding was not 

satisfactory. 

Figure 20: Rubber absorber test body, ready for testing 

2.4. PROTOTYPE 3 (GRASS PAVER) 

In version 3 grass paver replaced the upper 5 cm thick layer of the concrete beam and reached 

up to the rubber jacket. The foil was put, with difficulties, into a slot within the rubber jacket. 

The rest of the foil was glued to the concrete beam by means of Sikaflex. The bonding was not 

good enough though, so the foil already came off during installation of the vegetation system. 

Figure 21: Prototype version 3, grass paver up to rubber jacket, surrounding the rail





Figure 22: Test body with grass paver up to rubber jacket, ready for testing





3. DESCRIPTION OF PROTOTYPES WITH ARTIFICIAL GRASS 

3.1. ARTIFICIAL GRASS 

Artificial grass finishing has the following advantages : 

• possibility to install on existing track 

• low grass maintenance 

• fast and easy installation 

• permanently green 

• low life cycle cost compared to natural grass 

• good noise absorption 

• improved quality of last generation artificial grass 

The technical specification of the high grade artificial grass CDM used for the prototypes are : 

Fibres 100% polyamide, 14.000 dtex 

Number of knots/m² 17 640/m² +/- 10% 

Number of filaments/m² 400 000/m² +/- 10% 

Strength of fibres 315N (Pr EN 13864) 

Recuperation of fibre after bending 83,5° after 60 min. 

Height of fibres 38 mm +/- 5% 

Shrinkage height 15 min. at 150°C 2 mm 

100% monofilament (straight and curled) 

Withdrawal force fibres 47N (ISO 4919, BS 5229) 

Fixation of fibres Latex rubber 

Total weight 3 364 gr/m² +/- 5% 

Filling No filling necessary 

Colour Green (4 ranges of colours) 

Colour fastness Scale 7 (DIN 54004) 

UV-Stability > 6000 hours (DIN 53387)





Chlor resistance 4-5 (DIN 54019) 

Resistance to sea water 4-5 (DIN 54007) 

Water permeability 6e4 m/sec 

Inflammability Class 1 (DIN 51960) 

Toxic fume emission None ITC = 33 (NF X 70-100) 

Acoustic absorption coefficient 0,54 at 2037 Hz (tube of Kundt test, 

ISO 10534-1) 

For the gluing of the grass a Polyurethane based adherent was used. Figure 23 shows the very 

realistic looks of the artificial grass. 

Figure 23: Looks of a high grade artificial grass sample 

3.2. TRACK DESIGN 

The global track design which will be used for the validation track in Brussels (SP 3.2) is shown 

in figure 26. The jacketed rails are embedded in the concrete slab which is covered with the 

artificial grass layer. Rain water drainage is guaranteed via sideward inclination of the slab 

surfaces.





Figure 24: Cross section of track construction with artificial grass surface layer 

3.3. ARTIFICIAL GREEN TRACK PROTOTYPES 

Four test blocks with two different types of artificial grass finish (high grade with a very 

realistic look and lower grade grass) and two different adherence techniques (glued on concrete 

slab and integrated into the fresh concrete) were made for testing on the STUVA ring. When 

putting the artificial grass layer directly in the fresh concrete, metal sheets were placed along 

the sides of the jacket to protect them against mechanical deterioration by the occasional road 

traffic. 

Figure 24 shows the metal works construction and glueing of grass on a test block which will fit 

in the STUVA test ring set up for prototype testing. 

Figure 24: Test block construction and grass application process





Version 1: Artificial grass -5mm top of rail (TOR) - rail perpendicular wheel 

2 types of artificial grass were used for this test body: low density and high density. One rail has 

metallic plates to protect the jacket, the other one has not. This way the difference can be 

compared after the test. 

Figure 25 Version 1 

Version 2: Artificial grass -5mm TOR – rail longitudinal wheel 

The rail is placed in the same direction as the direction of the wheel of the test circuit. Metal 

plates are used to protect the jackets. Only high density grass is tested.






Version 3: Artificial grass glued TOR - rail perpendicular wheel 

2 types of artificial grass were used for this test body: low density and high density. No metallic 

plates are used. 


Version 4: Artificial grass -5mm TOR – rail longitudinal wheel 

The rail is placed in the same direction as the direction of the wheel of the test circuit. No metal 

plates are used. Only high density grass is tested.






The four blocks were finaly shipped to STUVA for wear testing. 

Figure 29 Prototypes before transport to STUVA





4. TESTS AND ACTION PERFORMED 

4.1. PRE-CULTIVATION 

During the pre-cultivation process of Sedum in grass paver several questions of practical 

realizations appeared and have to be solved. Focus is being laid on an economic production 

process to simplify pre-cultivation for further test zones. For further details see D1.3 (2008). 

4.2. FATIGUE TESTS 

The fatigue test at STUVA in Cologne is supposed to test the interaction of the system parts 

under the load of a lorry wheel. This simulates the use of the system by emergency vehicles for 

instance over 10 years. 

Figure 30: Fatigue test at STUVA 

Tested were: the fatigue of the whole system and its single components as well as their 

interaction. For further details and results see D1.3 (2008).





5. TESTS AND ACTION PLANNED 

5.1. NOISE MEASUREMENTS AT BRUSSELS TEST SITE 

At Brussels test site different track designs are going to be tested for noise absorption behaviour 

at 4 different zones. Three Sedum versions and one artificial grass version are planned to be 

installed and tested. Placing these zones right next to each other a comparison of the noise 

absorption behaviour at probably exactly the same conditions can be made.





6. PROBLEMS ENCOUNTERED 

IASP 

During the fatigue test the drainage material had to be changed, as both split and gravel were to 

similar in grit size and therefore not compressible enough. This caused loss of time, with the 

effect that firstly only 2 prototypes (version 1) were being tested properly and secondly that this 

test only comprised 4600 wheel crossings. Consequently not all test questions have been 

answered. 

No suitable grass paver for our pre-cultivation purposes is on the market. Producers are not 

interested in developing a new design at the moment, because of high costs for a new mould. 

Moreover, an industrial bonding of the foil to the sides of the track is needed. It is being tested 

at the moment if a pre-cultivation without fleece was feasible. 

CDM 

None.

deliverable d1.4 small prototypes of green tram tracks ... - urban track

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