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TIP5-CT-2006-031312 of 53URBAN TRACK Issued: 15/11/2010

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DELIVERABLE D0602. FINAL CONSOLIDATED REPORT -

CHAPTER 2

Related Milestone

CONTRACT N° 031312

PROJECT N° FP6-31312

ACRONYM URBAN TRACK

TITLE Urban Rail Transport

PROJECT START DATE September 1, 2006

DURATION 48 months

Subproject SP6 SP6

Work Package WP6.2 Consolidation

Technical consolidation report on all validationresults (Chapter 2)

Written by Yves Amsler and Caroline Hoogendoorn UITP

Date of issue of this report 15/11/2010

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 ander 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

Ferrocarril Metropolita de Barcelona TMB ES

Transport Technology Consult Karlsruhe TTK DE

Université Catholique de Louvain UCL BE

Universiteit Hasselt UHASSELT BE

Project funded by theEuropean Community undertheSIXTH FRAMEWORKPROGRAMMEPRIORITY 6Sustainable development,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

Frateur de Pourcq FDP BE

Lieve Vanherwegen

Approved



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

2. Cost effective track maintenance, renewal & refurbishment methods (SP2) ..........................................4

2.1. New low cost renewal and refurbishment methods: Description of tracks with regard

to renewal and improvement possibilities (WP2.1, developed by STUVA) ...................................4

2.1.1. Basic Rules for efficient low-cost-criteria ..................................................................................4

2.1.2. Recommendations for Refurbishment and renewal of single track elements ........................5

2.1.2.1. Rails .........................................................................................................................................5

2.1.2.2. Switches ..................................................................................................................................5

2.1.2.3. Rail Fastenings........................................................................................................................6

2.1.2.4. Sleepers ...................................................................................................................................6

2.1.3. Recommendations for packing cleaning and recycling of ballast ...........................................7

2.1.4. Recommendations for track design...........................................................................................7

2.1.4.1. Optimisation of design conditions ........................................................................................7

2.1.4.2. Change from ballast track to slab track.................................................................................7

2.1.4.3. Specific design criteria for concrete slabs .............................................................................8

2.1.4.4. Specific design criteria for tracks on steel viaducts..............................................................8

2.1.4.5. Special measures for track transitions...................................................................................8

2.1.4.6. Selection of the most efficient solution .................................................................................9

2.1.5. Recommendations for noise and vibration protection.............................................................9

2.1.5.1. Observation of basic rules......................................................................................................9

2.1.5.2. Avoidance of over-design......................................................................................................9

2.1.5.3. Adoption to local situation ..................................................................................................10

2.1.5.4. Combined measures for ballast tracks ................................................................................10

2.1.5.5. Additional noise reducing measures on slab tracks...........................................................10

2.1.5.6. Rail grinding important for noise reduction.......................................................................10

2.1.5.7. Curve-squeal mitigation ......................................................................................................11

2.1.6. Recommendations for fire and rescue issues..........................................................................11

2.1.6.1. Improved self rescue requirements.....................................................................................11

2.1.6.2. Horizontal exit/entry conditions ........................................................................................11

2.1.6.3. Avoidance of toxic gases......................................................................................................11

2.1.7. Recommendations for occupational safety and health considerations.................................12

2.1.7.1. Hazards and provisions.......................................................................................................12

2.1.7.2. General measures to minimise hazards ..............................................................................12

2.1.7.3. Specific safety measures on bridges with embedded or segregated tracks......................13

2.1.7.4. Specific measures in tunnels and on viaducts ....................................................................13

2.1.7.5. Specific measures for driverless metros..............................................................................13

2.1.8. Tests on a test circuit and hydro-pulse-facility for embedded tracks ...................................14

2.1.8.1. Description of the test facilities............................................................................................15

2.1.8.2. Description of the test bodies embedded in road surfaces ................................................16

2.1.8.3. Conducting the tests on the test circuit...............................................................................17

2.1.8.4. Conclusion ............................................................................................................................21



2.2. Optimal maintenance methodology (WP2.2)..................................................................................23

2.2.1. Visual inspection & maintenance (WP2.2.1, developed by FCP) ..........................................23

2.2.1.1. Introduction..........................................................................................................................23

2.2.1.2. Strategy used and description of the methods ...................................................................23

2.2.1.3. Results ...................................................................................................................................23

2.2.1.4. Conclusions...........................................................................................................................26

2.2.1.5. Bibliography .........................................................................................................................27

2.2.2. Predictive and preventive maintenance of metro tracks

(WP2.2.2, developed by INSA, INRETS and D2S)..................................................................28

2.2.2.1. Understanding rail lubrication impact

(WP2.2.2a, developed by INSA) ..........................................................................................28

Conclusions .......................................................................................................................................29

2.2.2.2. Solving the problem of rail track reliability estimation

(WP2.2.2a, developed by INRETS)......................................................................................34

Background ...........................................................................................................................................34

Probabilistics Graphical Models ..........................................................................................................35

Definitions .........................................................................................................................................35

CPD parameters learning .................................................................................................................35

Inference in PGMs.............................................................................................................................36

Dynamic probabilistic graphical models.............................................................................................36

Introduction of the Graphical Duration Models .................................................................................38

Qualitative definition........................................................................................................................38

CPDs definition.................................................................................................................................39

Reliability analysis using GDM............................................................................................................41

Basic definitions ................................................................................................................................41

Reliability...........................................................................................................................................41

Failure rate.........................................................................................................................................42

Mean Time To Failure (MTTF).........................................................................................................42

Conclusions .......................................................................................................................................42

Estimation method................................................................................................................................43

Application to track reliability estimation...........................................................................................45

Variables definition...........................................................................................................................45

CPDs learning ...................................................................................................................................46

Results................................................................................................................................................47

Conclusions and Perspectives..............................................................................................................48

2.3. Advanced maintenance strategies (WP2.3 developed by TTK)....................................................50

2.3.1. Introduction ..............................................................................................................................50

2.3.2. Methodology.............................................................................................................................51

2.3.3. Conclusions...............................................................................................................................53

General tendencies regarding track management ..........................................................................53



2. COST EFFECTIVE TRACK MAINTENANCE, RENEWAL &REFURBISHMENT METHODS (SP2)

The sub-project SP2 focuses on existing tracks and deals with cost effective track maintenance, renewal &

refurbishment methods. It covers the following sub-packages:

new low cost renewal and refurbishment methods for track (WP2.1)

optimal maintenance methodology (WP2.2), divided in three sub-packages:

o visual inspection and maintenance (WP2.2.1);

o predictive and preventive maintenance of metro tracks (WP2.2.2);

o preventive maintenance of embedded tram tracks (WP2.2.3)

advanced maintenance strategies (WP2.3).

Recommendations from this chapter are validated in chapter 3 (chapter 3.5, Bremen) and are an input for

chapter 4 on LCC and chapter 5 on definition of functional requirements and functional specifications for

tram and metro track.

2.1. NEW LOW COST RENEWAL AND REFURBISHMENT METHODS: DESCRIPTION OF

TRACKS WITH REGARD TO RENEWAL AND IMPROVEMENT POSSIBILITIES (WP2.1,DEVELOPED BY STUVA)

The recommendations for tunnels and viaducts exemplarily are shown in the following. In principle

similar recommendations were worked out also for the two other kinds of tracks (tracks with separate

right of way on the surface and embedded in roads). Typical tracks in roads were examined with regard

to duration long-lastingness at a test facility (circuit) in the STUVA. Green tracks were also checked with

regard to traffic ability due to vehicles of the police, the fire brigade and of ambulances at this test facility.

These results are summarized in report D2.11 (see Chapter 2.1.8).

The validation site has been Bremen, Germany, see chapter 3.4 and 3.16.

2.1.1. Basic Rules for efficient low-cost-criteria

The following basic rules for a definition of efficient low-cost-criteria should be observed:

There can be no “one-design-fits-all” solution for urban tracks. An optimal and economical track design is

always adapted to exactly defined local conditions. Above all, low cost solutions shall not lead to poor

quality solutions.

Therefore “efficient low-cost” can only mean: “select under given framework and quality conditions the

appropriate technical solution, which leads to the lowest possible costs over the entire lifetime of the

system (LCC), while considering all mentioned individual cost factors from planning and constructing

until disposal.”

The following recommendations therefore offer for most conditions and interdependencies a “modular

system” of solutions with their economical aspects.



2.1.2. Recommendations for Refurbishment and renewal of single track elements

2.1.2.1. Rails

Removed vignole rails in an open superstructure should always be examined for re-use after

reconditioning (rail realignment or re-profiling). Such reconditioned rails may be used in track

categories/sections with lesser operating loads or lower running speeds (e. g. outer branches of lines;

yard tracks etc.). Reconditioning of vignole rails normally creates economic advantages compared with

the use of new rails.

Because replacement of rails in open tracks normally is relatively easy to practice, other rail refurbishing

methods such as rail resurfacing by welding or the use of high-grade steel qualities for rails (e. g. head

hardened rails) in most cases is not an economic solution in tunnels and on viaducts. Only when (e.g. as

often practised on bridges) the rails are embedded in the structure/floor slab, these measures should be

taken into account. In such cases extended rail service life can lead to lower LCC-costs compared to the

exchange of rails (for further details see Deliverable D 2.3 “Embedded Tracks”).

2.1.2.2. Switches

Switches are subject to heavy stress and high levels of wear. On economic reasons, the number of

switches should be limited to the absolute necessary requirements for a flexible train operation especially

in case of failures or breakdowns. Complex systems (e. g. double switches) procure high maintenance

costs and should therefore be avoided as far as possible. Standard switch solutions using uniform

components should be selected with priority and for low cost reasons.

Consideration of both, technical and economical criteria, suggests observing the following rules for

switches in all track types:

The rail profile of a switch being installed should correspond to that of the connecting tracks.

Switches with a larger diverging track radius are longer and more expensive, but allow vehicles to

travel at higher speeds on the diverging track and are less susceptible to wear. Consequently,

switches with a larger radius should be used if they are to be passed through frequently by scheduled

services.

Where possible, vehicles should be able to cross-branching switches in main lines on the diverging

track at the speed permitted on the adjacent track.

To avoid mutual disruptions during installation and subsequent replacement works, the switches should

be configured independently of each other and not 'overlap' with sleepers on adjacent tracks.

Switch tongues of vignole rails in open tracks should be exchanged rather than reconditioned by

welding, because the open position allows that the tongue blade can be replaced easily and quickly,

without interrupting train service.

Because switches are highly complex, their installation, repair, or exchange on site is expensive and

labour intensive, especially in tunnels and on bridges. Pre-assembling of switches in the factory with

extreme precision and in parts, enabling them to be installed on site as fast as possible, but still



transportable, and with minimal operational disruptions is therefore a precondition for efficient low cost

solutions.

To optimize switch maintenance it is recommended to install interdisciplinary maintenance teams. The

aim is a replacement of preventive or corrective maintenance with a condition-driven approach that is

only applied when and where necessary. This leads to the most economic solution. Full replacing of

switches is very expensive and time- and labour intensive. It should be avoided as far as possible.

2.1.2.3. Rail Fastenings

The kind of rail fastening system used for specific applications influences remarkably track’s static

stiffness, precision of rail alignment, load distribution, stray current insulation, noise and vibration

emission and therewith travel comfort. Because these requirements gain increased importance in urban

transport, indirect rail fastening systems should be preferred today. These fasteners offer the possibility

to adapt the insulation and deflection criteria of the track bed within given limits to specific local

demands, which is of high economic importance with reference to refurbishment and renewal works.

Especially for urban railway tracks, it is of high importance today that the selected rail fastening system

consists of the fewest possible parts and allows pre-assembling (e.g. on sleepers or on prefabricated

concrete elements) before being delivered to the place of installation. This enhances the quality of

construction and reduces on site assembly time and costs, especially for use with slab tracks.

Whenever in tunnels and on bridges the limit values for noise and vibration emission can be reached by

specific rail fastening designs, this has proved the most economic solution compared with all other

measures. Continuous, elastic rail fastenings (perhaps based on new and successful solutions for

embedded rails) should be taken into account also for tunnels and bridges.

For service and economic reasons, the exchange of rails and rail fasteners should be coordinated and

realized at the same time wherever possible.

2.1.2.4. Sleepers

Because of increasing legal restrictions for the use of impregnating materials and also for economic

reasons (LCC), wood sleepers should be replaced by pre-stressed reinforced concrete sleepers, whenever

refurbishment or renewal measures are necessary in urban transport. Especially in tunnels, this

additionally reduces fire risks and release of toxic gases.

The lower axle loads in urban transport make lighter pre-stressed concrete sleepers sufficient. For

example, the use of bi-block sleepers has proved technically and economically advantageous, preferably

in conjunction with renewal as slab track.

Solutions with polymer concrete sleepers, Y-steel sleepers and plastic sleepers (PUR) embedded in

concrete are exceptions in urban transport so far. The latter may gain some further importance with

respect to the reduction of noise and vibrations and better electrical insulation.

Replaced reinforced concrete sleepers should always be examined for re-use. Quality tests decide,

whether they can be used in normal tracks or in sections with lower loads. Reconditioning of sleepers

creates ecologic and economic advantages compared with the use of new sleepers.



2.1.3. Recommendations for packing cleaning and recycling of ballast

As the ballast bed grows increasingly contaminated in course of time, the pressure dispersion angle

below the sleeper decreases, which can lead to uneven loads on the track formation and thereby, in

certain circumstances, to shifting and settling. Besides that, the ballast bed loses elasticity and

permeability. As a result, regular inspection of the track and cleaning of the ballast (if necessary) are

required.

Because packing (tamping) is one cause of destruction of ballast grain and particle disintegration the

number of packing operations is limited before ballast cleaning or replacing is needed. Tamping can raise

the rail level. This also can be a reason for bedding cleaning. Bedding cleaning is normally required after

about 35 years.

In tunnels, additional safety aspects need to be considered. Light waste materials (such as leaves, paper

and so on) are scattered by draughts into the wider areas just before stations or into any niches, where

they settle and become a fire threat. Their regular removal e. g. with suction machines is thus required for

fire protection reasons.

In urban public transport systems, the dense network of stops and frequent halting at signals (due to both

railway signals and traffic lights, etc. on roads), the risks of pollution of ballast (e. g. by fuel and

lubricants) are far higher than on the railways in general. This can lead to a higher intensity and

frequency of cleaning and thus also impacts on profitability.

Almost all regulations in force today recommend recycling of contaminated ballast. In urban public

systems, the cleaning of ballast in mobile facilities close to the construction site and the re-use as lower

ballast layer on renewed tracks has proved the most economical procedure. However: Several

environmental rules must be observed when disposing, cleaning and re-using ballast with (perhaps)

restricted application.

2.1.4. Recommendations for track design

2.1.4.1. Optimisation of design conditions

Urban railway tracks in tunnels and on viaducts are completely independent of other traffic (not always

on bridges). The substructure is the tunnel or viaduct construction, which form a solid (normally

concrete) and settlement-free base for the superstructure of the track. These conditions are ideal and

allow a relatively free choice of track design. This situation should be used to optimize the design

technically and economically to the specific conditions of the particular application.

2.1.4.2. Change from ballast track to slab track

In tunnels and on bridges a change from ballast track to slab track is recommended, whenever renewal or

refurbishment measures are necessary. This has especially two reasons:

Due to narrow spaces, repair and maintenance works are difficult to carry out and should therefore

be limited as far as possible;

On escape and rescue reasons in case of fire a solid track bed with even surface is of high importance.



Under these circumstances, the higher investment costs of slab tracks are justified especially in tunnels

and on bridges.

When using floating-slab-systems, along term effective and easily accessible drainage is of crucial

importance for the long term functioning, therewith avoiding water accumulation and sintering effects in

the joints with the elastomeric layer.

2.1.4.3. Specific design criteria for concrete slabs

When using concrete slab tracks or floating-slab-systems in tunnels and on bridges important design

criteria have to be observed:

The slab always has to be separated from the substructure by an elastic layer (reasons: separate

freedom to move; vibration protection). To avoid longitudinal sliding of the slab when breaking (of

trains), special anti-shear-devices (such as cams or anchors) need to be installed at pre-defined places

of the structure.

Protection against stray currents of any reinforced concrete parts is important to observe, e. g. by

interconnection of the reinforcement mats of the individual concrete elements.

When using floating-slab-systems, along term effective and easily accessible drainage is of crucial

importance for the long term functioning, therewith avoiding water accumulation and sintering

effects in the joints with the elastomeric layer.

The observation of these criteria is strongly recommended, because they are of high importance for the

durability of the structure (avoidance of damages) and thereby influences life-cycle-cost remarkably.

2.1.4.4. Specific design criteria for tracks on steel viaducts

A new and effective solution for steel viaducts is the direct placement of rails on the steel structure (e.g.

on longitudinal beams) by highly elastic rail fasteners. It is of crucial importance in such cases, to realize

possible longitudinal movements of the rail (e.g. sliding on Teflon elements), independently from the

viaduct structure to avoid uncontrolled load distribution. Only on exactly defined and placed fixed

support points the longitudinal forces should be distributed (controlled) via the bridge structure to the

foundation.

Corrosion protection measures connected with refurbishment works should on economic reasons be

adjusted to the individual extend of damages. Besides the application of specific coatings, the electric

interconnection of the different steel elements of the viaduct (avoidance of stray current corrosion) and an

effective drainage of the steel structure (avoidance of water accumulation) has to be observed.

2.1.4.5. Special measures for track transitions

Track transitions from both slab tracks to ballast superstructures and from engineering structures (tunnel,

bridge) to earth structures need specific measures. It is recommended to focus special attention to these

sections of a track way.



Especially the areas of engineering and earth structures may differ starkly in subsidence behaviour

(danger of deformation and/or formation of ledges). An adoption in rigidity is therefore needed in the

transition sections, e. g. by graduated cementing of the critical backfill areas or by using a transition slab.

Transitions from one track type to another should not take place in curves and not come directly after

switches and crossings.

2.1.4.6. Selection of the most efficient solution

The “most efficient” solution for a railway track must always observe technical and economical aspects as

well as local requirements and the interests of line-side residents (e.g. adjacent to viaducts). One-sided

optimisation cannot fulfil the demands of the train operator and other involved parties.

The planning engineer’s knowledge of the cost relations for different track designs is (independent from

real investment cost values) of high importance, because this can lead to the technically and economically

most efficient solution for exactly defined local framework conditions.

Of special importance for complete renewal of public rail tracks (especially on viaducts and bridges) in

densely build up urban areas are henceforth:

The early participation of all involved parties;

A perfect neutral (and external) project management;

An open minded and transparent public relation work by humanly and professionally competent

persons, placed directly on the building site;

High quality contractors;

The exact observation of (mostly) tough time schedules.

Only such “joint efforts” can result in an overall success of the measure.

2.1.5. Recommendations for noise and vibration protection

2.1.5.1. Observation of basic rules

To reduce vibration effects it is of high importance to observe two basic rules:

The natural frequencies of the ceilings in the (line adjacent) buildings should be measured. The track

bed should have another natural frequency to avoid resonance effects in the ceilings.

The support point spacing of the rail in the track bed should not be a multiple of the distance

between the wheels of the vehicle, to avoid any “build up” of vibrations in the wheel set.

These rules lead to the following recommendation: track bed design should always be adapted to vehicle

and design of adjacent buildings to reach best possible vibration abatement effects.

2.1.5.2. Avoidance of over-design

For urban railway tracks in tunnels and on bridges, noise and vibration protection is a feature, which

gains growing importance. It is therefore a cause for renewing or refurbishment works. But the technical



solutions show a great variety of possibilities and differ largely in costs. Therefore, the measures should

be strictly adjusted to the real demands of the given situation on different track sections. These may

change in the course of a line. The tendency to the use of one single-track design (e.g. floating-slab-track)

for the worst-case section on the whole line length is the most expensive solution and should be avoided.

2.1.5.3. Adoption to local situation

Depending on the sensitivity of the vicinity of the track way (adjacent buildings and their utilisation etc.)

the application of vibration protection measures can be roughly recommended. The vibration reduction

increases and the associated track building costs approximately rise correspondingly (from perhaps

factor 1 to factor 4). The observation of these cost/benefit relations is therefore strongly recommended.

2.1.5.4. Combined measures for ballast tracks

A promising new development (test phase) is the stabilization of old or new ballast superstructures by

polyurethane (PUR) in the load distribution area underneath sleepers. It compensates most of the

disadvantages of normal ballast superstructures Furthermore, it reduces vibration and noise emissions.

Exact measurement results are expected from an urban track application in Berlin.

For an application of polyurethane-stabilized ballast systems in tunnels, results of specific fire-tests are

still needed. They should especially deal with temperature loads, fire-resistance and –distribution, release

of toxic gases, generation of combustion products (smoke gases) etc.

2.1.5.5. Additional noise reducing measures on slab tracks

Compared to a ballast track bed with sleepers a slab track bed is associated with higher airborne noise

emissions (up to + 5 dB(A)). If these lead to an exceeding of the limit emission values, further noise

reducing measures need to be considered. Two possibilities can be recommended:

Absorbent plates as cover of the slab track way (reduction of noise emissions by some 2 to 3 dB(A));

Acoustic barriers (low walls with sound absorbing materials) running next to the track (attenuating

effect up to 5 dB(A), depending on the situation).

Whilst the first solution is applicable both in tunnels an on bridges/viaducts, the second solution is more

likely for bridges and viaducts, because there it affects the path of noise propagation most effectively.

2.1.5.6. Rail grinding important for noise reduction

The total noise emitted by wheels and rails is largely determined by the roughness of both running

surfaces. Regular grinding of the rails is therefore of high importance for low noise (and vibration)

emissions. Due to great weight the best grinding results are reached with rail-bound grinding machines,

but they can only be deployed at night time so far, when no services are in operation (low running

speed). A new focus is there for laid on “high-speed” grinding machines, which can nearly operate nearly

at the same speed as the services. A continuous grinding during regular service is therefore possible, thus

avoiding corrugation already in the developing stage and preserving a good condition of the rail surface.



2.1.5.7. Curve-squeal mitigation

The most troublesome noise in urban rail transport is curve-squeal. It is very difficult to avoid, because it

results from the stick-slip-effect of the wheel on the rail. Especially if the difference between the static and

sliding friction values can be considerably reduced the typical tonal curve-noise is largely avoided.

The following measures have proved effective and applicable in tight curves of segregated tracks:

Lubrication of the wheel-rail-contact area (but observe necessary breaking characteristics of vehicles

and avoid over-lubrication);

Damping the rail flange by specially designed rail dampers of elastic material (especially on existing

tracks).

2.1.6. Recommendations for fire and rescue issues

2.1.6.1. Improved self rescue requirements

When tracks in tunnels and on bridges are due for renewal or refurbishment, fire and rescue issues are

another key factor to observe. That means: The options for self-rescue and assisted rescue for all

passengers (also for those with disabilities or reduced mobility = barrier-free-design) and for the crew

should be improved to the greatest extent possible. This is a difficult demand and not to fulfil in all cases

and at all circumstances. Especially in tunnels a solid and even (step-free) slab track design using fire-

resistant (low fire-load) materials and easy-to-clean surfaces (= no combustible waste in track bed) is of

high importance.

2.1.6.2. Horizontal exit/entry conditions

Track design in tunnels and on bridges should allow adjusted vehicle floor and platform heights at stops,

to achieve nearly horizontal exit/entry and therewith optimal self-rescue conditions, when damaging

event occur (e. g. fire, power outages, derailments, crashes). Such optimization has implications for track

design and maintenance; in particular: regular checks and track refurbishment/renewal at earlier limit

values of wear, to avoid unacceptable step heights and gap widths at the “interface” between vehicle and

platform.

2.1.6.3. Avoidance of toxic gases

In tunnels, components of emergency walkways and crossings, wooden sleepers, elastic damping

elements, switch cabinets, escape route signs, fasteners made from plastic or rubber, etc must not to any

significant degree release toxic gases or generate combustion products with greater hazard potential than

ordinary smoke gases in the event of fire.

Sheathing on cables must prevent fire from breaking out (short circuiting or overheating) and not

generate any toxic substances. During renewal and refurbishment works, materials and equipment,

which are not state-of-the-art in terms of safety risks, should be replaced.



2.1.7. Recommendations for occupational safety and health considerations

2.1.7.1. Hazards and provisions

Works on a railway track (especially in the traffic area shared with other motor-vehicle traffic as

sometimes on bridges) entail various hazards for the personal working within the track (e. g. from train

operation, motor-vehicle traffic, construction site traffic as well as from the general running of the

construction site). Therefore, special measures must be taken to protect the workers and to ensure, that

rail operation is not jeopardised by large construction-site equipment.

For occupational safety and health measures, an EU harmonisation is currently sought in the form of

minimum requirements. As a result, national accident-prevention measures are increasingly being

replaced by EU regulations. These have to be observed and no national standards are allowed to fall

below the EU minimum level.

2.1.7.2. General measures to minimise hazards

A thorough safety planning, consisting of organisational, technical and personal measures, is of vital

importance. For most sites of renewal or refurbishments a combination of such measures leads to the best

results.

Organisational measures consist of track closure, blocked runs or speed restrictions. Track closure should

be avoided in public transport due to significant disruption of train operation. Blocked runs are not

possible in public transport, because of short time intervals between passing train vehicles. Running at

sight and with low speed when passing construction site is the preferred and recommended measure in

public transport.

But observe: Organisational measures alone do not provide sufficient protection in most cases.

Technical safety measures include e. g. stop discs, barriers or light signals. In urban transport they can be

recommended in connection with low speed train running operation at sight.

The most important personal safety measures on small (and short-time) railway construction sites (e. g.

refurbishment works) are lookouts. They give an acoustic warning of approaching trains to those

working within the track.

But observe: Acoustic (and visibility) tests under the worst possible conditions (loud background noise)

should be conducted.

Where large-scale construction work is carried out (e. g. complete track renewal) a competent person for

safety supervision should be appointed, who defines and coordinates the safety measures between the

different parties.

As specific measures to reduce hazards from construction site traffic and the general running of the

construction site can be recommended:

Safety-oriented site organisation (especially definition and marking of free safety areas and escape

routes),

safety training and a binding code of conduct for the employees

as well as, observation (and supervision) of individual safety precautions.



2.1.7.3. Specific safety measures on bridges with embedded or segregated tracks

Besides the general measures, work sites with embedded or segregated railway tracks in roads on bridges

need additional technical safeguards against road traffic. A combination of e.g. lengthwise barriers,

beacons, lights and marking is often practised and can be recommended.

2.1.7.4. Specific measures in tunnels and on viaducts

Track works in tunnels and on viaducts can largely be carried out without direct contact with the road

traffic. But in contrast to track construction work at grade in streets some unusual features have to be

taken into account here:

Restricted conditions for the execution of work;

Restricted safety areas for the workers in case of danger;

In tunnels: Supplying of sufficient fresh air and fire protection;

Materials handling to the construction site must be executed lengthwise over the tracks etc.

Therefore the following safety precautions (additional to the general measures) have to be taken into

account:

considering whether for safety and rescue reasons the tunnels should be designed as two single track

tunnels with cross-connections at a distance between 300 m and 500 m instead of one double track

tunnel.

defining and marking of specific safety areas and keeping them free from other users.

establishing a specific working group for safety (persons from owner, safety organisation and

contractor), with focus on sagely precautions on the construction site.

definition of a detailed escape and rescue map for the construction site, coordinated with the local

fire brigade and based on a hazard assessment.

monitoring the concentration of harmful substances (e.g. dust, quartz, smog) in the tunnel air and

their reduction by an effective ventilation system.

2.1.7.5. Specific measures for driverless metros

If metro sections or lines are operated without drivers, measures must ensure that work in the track area

can be performed just as safety as during conventional operation with a driver.

Such measures are:

signal dependent protection systems;

conduction of work outside operating hours;

taking automatic train control out of operation during the works and having a person or a system

monitor the working section of the track.



2.1.8. Tests on a test circuit and hydro-pulse-facility for embedded tracks

Public transport tracks embedded in road surfaces are subject to the following stresses and

environmental conditions:

static and dynamic forces exerted by the rail vehicles;

loads caused by heavy goods traffic (lorries, buses);

changes in temperature, rain, brake sand, ballast chippings, frost.

These stresses very often cause damage at the interface between the embedded tracks and the road

surface. Figure 2.1.1 shows typical damage in this area.

Figure 2.1.1: Damaged contact areas between road surface and embedded track

This situation entails not only substantial repair costs but also restrictions on public local rail transport

and private motorised traffic while such track areas are reconditioned or renovated.

In practice, comparative studies of alternative forms of construction require years of observation, during

which time it is very difficult to ensure a largely identical load. Realistic test bed studies achieve both a

time-lapse effect and an equal load for all solutions being investigated.

The load on embedded tracks caused by passing lorry traffic was simulated at the STUVA test circuit. For

this purpose test-bodies incorporating a similar rail-bed and fastening-system structure but different road

surfaces were produced and installed in the test circuit. The structure of the test-bodies is described in

detail in 2.1.8.2. The tests yielded conclusions on the following problems:

the durability of the superstructure at the rail-road surface interface;

the influence of temperature;

comparison of the different road surfaces in terms of the damage symptoms occurring.

Against this background also the test bodies used for the later on described tests belong to this three

structure forms. All of them were realised in test-bodies. Additionally “green” track-bodies were also

tested.



2.1.8.1. Description of the test facilities

STUVA has a test circuit which can be used to investigate various problems with road surfaces. The

facility consists of a circular roadway on which two lorry wheels roll connected by an axle. The entire axle

load is transferred to the ‘roadway’ through the two wheels.

The axle is moved in the centre by a revolving turret. The latter is driven by an electric motor via a

turntable thereby causing the wheel axle to rotate. The axle has two side pivots in the centre: these engage

sliding blocks, which enable the axle to ‘rock’. The sliding blocks themselves can move vertically within

the revolving turret such that the axle and wheels can be raised and lowered by means of two hydraulic

cylinders.

The entire facility is located in a test hall, Figure 2.1.2, can be air-conditioned and is equipped with the

necessary safety systems; the facility is operated via a control panel outside the test chamber.

Figure 2.1.2: STUVA test circuit machine with the 16 test-bodies of embedded rails

Test-circuit specifications:

axle load Q = 10 t (= 100 kN; maximum with extra weight),

spacing of wheel centres d = 10 m;

wheel load Fwheel = 5 t (= 50 kN), air-cushioned, no transmission of acceleration and braking forces,

tyres: 445/65R22.5 (RHT 169K);

electric drive to a wheel speed of V = 100 km/hr;

temperature equalisation: -30°C to +60°C;

maximum test-body height: h = 40 cm.

16 Test bodies

Revolving turret, drive

Axle

Rubber-Wheels

Extra weight



2.1.8.2. Description of the test bodies embedded in road surfaces

In practice, embedded rails are subject to stress in different directions (transverse, longitudinal and

diagonal). Figure 2.1.3 shows two examples.

Figure 2.1.3: Transverse and longitudinal stress on rails embedded in road surfaces.

These loads can cause damage to the contact area of rail and carriageway surface.

In order to conduct practical tests, the test-bodies had to meet certain conditions:

be representative of various types of carriageways;

enable embedded rails to be driven over in the transverse and longitudinal direction;

be a certain height, length and width (measurements predetermined by the test facility).

The test-circuit carriageway ring was subdivided to accommodate 16 test-bodies to study eight different

types of carriageway, each with longitudinal and transverse embedded tracks.

Two test-bodies were sawn out of a track base plate (pre-cast concrete product with embedded rails) and

thus delivered in the required dimensions. For the other test-bodies, 14 trapezoidal steel frames were

made, which served as side formwork for both the concrete substructure and the differing structure of

asphalt, paving and concrete. After the 14-cm high supporting slab was filled with concrete, the rails

were installed in such a way as to reflect actual usage as far as possible and using the fasteners currently

used in practice. All bodies share a continuous-elastic rail bed on the supporting concrete slab.

Figure 2.1.4 outlines the numbering of the various test-bodies.



Testbody Type Supplier

1 + 2 Concrete covering GVB

3 + 4 Mastic asphalt Edilon)(Sedra

5 + 6 Concrete surface Hastra, Regum

7 + 8 Unbounded paving Hastra, Regum

9 + 10 Bounded paving Hastra, Regum

11 + 12 Asphalt surface Hastra, Regum

13 + 14 Concrete with corkelast Edilon)(Sedra

15 + 16 Modulix system CDM

Figure 2.1.4: Overview of the arrangement of the 16 test-bodies in the test circuit

The production of the test-bodies does not correspond to the possibilities on the spot in every case. This

applies particularly to all test-bodies which are condensed at the installation place (asphalt) or need a

special underground (stones). The installation possibilities are limited by the soft steel sheet formwork of

the test-bodies, too. This has to be taken into account at the assessment of the results.

The test-bodies were positioned appropriately using the test hall's ceiling crane and fastened by steel

braces on a level concrete base course. They were arranged horizontally and vertically to achieve a largely

level running surface (no height differences or gaps between the test-bodies) and thereby enable the

facility to run quietly.

2.1.8.3. Conducting the tests on the test circuit

Before the tests were performed on the test circuit, the following had to be ascertained:

the test sequence for before/after comparisons;

what measurement data should be recorded;

how they were to be recorded and evaluated;

the nature and scope of documentation;

the time required.

The structure of the test-bodies and the course of the tests were coordinated with the participating

transport companies from Karlsruhe and Bremen and the test-body suppliers. The test-bodies themselves

were supplied free of charge by the track-construction companies.

In order to assess the resistance of the various combinations of track types, a minimum lifecycle of 10

years had to be simulated. An average daily load for heavy goods vehicles of 100 3-axle vehicles was

assumed. Accordingly, over 10 years:

300 axles/day • 3,650 days = 1,095,000 wheel crossings.

The desired 1,000,000 or so wheel crossings were to be performed at a speed of 50 km/hr as customary in

towns. The following results were obtained:



A diameter of 10 m yields a path length of 31.4 m on the test ring. Where V = 50 km/hr (= 13.9 m/s), a

time of t = 2.26 s is recorded for one rotation (= two wheel crossings). At 2.26 s x 500,000 rotations, the

estimated theoretical run time of the test circuit is T = 1,130,000 s

( 313 hours). Based on 40 operating hours per week (= eight hours per day), the planned time required is

approximately eight weeks. The total test duration, factoring in required facility-maintenance time, was

approximately 10 weeks.

To ensure that the tests were based on as realistic a scenario as possible, air temperatures of

-10°C, +10°C and +30°C were chosen so that the thermal loads on the test-bodies corresponded

approximately to outside environmental conditions in Central Europe. The total required test time was

divided into three cycles. In each cycle, the air temperature was altered in line with the predetermined

criteria (Figure 2.1.5).

Figure 2.1.5: Change in room temperature in the test hall during tests (circuit machine)

Prior to first use and after each cycle, the surfaces of the test-bodies were scanned with a laser to identify

any possible changes in the rail bed and the rail/carriageway contact area.

The procedure below was followed during testing:

test-bodies installed in the test circuit;

carriageway surfaces scanned in a longitudinal and transverse direction with a laser;

test circuit: test cycle 1;





carriageway surfaces scanned in a longitudinal and transverse direction with a laser.

Measurement of the „pavement‘s“ surfaces

0 1 2 3

Cycle 1 Cycle 2 Cycle 3

pouring water



The main tests in the test circuit took place during the periods 21 February to 7 March, 2 April to 6 May,

and 29 May to 11 June 2008. Testing had to be halted on the first occasion to enable replacement of two

test-bodies which had failed to withstand the loads), while on the second occasion, maintenance was

required on the test circuit. At various points, some test-bodies had to be subsequently stabilised to

ensure that the facility remained stable. Overall, on average some 24,000 wheel crossings per day were

achieved.

Each day, the test circuit was inspected prior to testing and all test-bodies examined and checked for

visible damage. During the first few days, at -10°C and +10°C only slight surface abrasion and a small

amount of displacement of the rail joint compound were observed. After the air temperature was set to

+30°C during the first cycle more noticeable displacement of the rail joint compound was observed; at

this temperature, the compound became very soft. During operation, the tyres reached temperatures of

approximately 60°C and joint compound adhered to them; stuck to the tyres, the joint compound was

thus distributed across all test-bodies. Test bodies 7 and 8 (bituminous-sealed paving stones on a layer of

chippings) were particularly affected by displaced rail joint compound (Figure 2.1.6 left).

Figure 2.1.6: Displacements on test-bodies 7 and 8 at 30°C during the first cycle (left), Deep travel groove on the

asphalt running surface (right)

As a result of this damage, test-bodies 7 and 8 had to be removed and replaced by ‘dummies’.

On the test-bodies incorporating an asphalt running surface, increasing indentation of the travel grooves

was observed (Figure 2.1.6 right), whilst concrete surfaces and paving stones sealed with special mortar

behaved in a very stable manner.

All elements are similar in that the rails did not move within the test body. Similarly, the damage to the

compounds, regardless of its scale, occurred during the first test cycle in all elements, i.e. within a

simulated life cycle of approximately three years.

During the third cycle, the surfaces were iced at -10°C. The temperature was briefly lowered to -15°C and

the surfaces of the test-bodies were sprayed with water repeatedly to produce a layer of ice several

millimetres thick. However, no noticeable effect was observed in any of the test-bodies when the load

exerted by the wheels was applied again at -10°C following this brief stoppage.



Test bodies 5 and 6 (concrete surface C30/37, concrete substructure) proved particularly stable. By

contrast, test-bodies 7 and 8 (large granite cobblestones, unbound with bituminous joint compound,

concrete substructure) were less resistant. The results indicate that granite pavement is only suitable for

use in tracks often driven over by buses and lorries when combined with special mortar compound. In

addition, concrete rather than asphalt should be used in areas of road/rail contact. Table 2.1.1 outlines

further recommendations.

Carriageway structure Load by bus/lorry traffic

Test bodies Rail without low1) medium2) high3) Comments

1/2 Concrete Ri 59N X X X X

3/4 Mastic Asphalt Ri 59N X X X - Sensitive at high

temperatures

5/6 Concrete, S49 X X X X

7/8 Paving, unbound Ri 59N X - - - Sensitive at high

temperatures

9/10 Paving, bound Ri 59N X X X -

11/12 Asphalt Ri 59N X X - - Sensitive at high

temperatures

13/14 Concrete solid

bodies

Ri 59N X X X X

15/16 Modulix system Ri 59N X X X X

1) < 10 passes per day ; 2) to 50 passes per day; 3) > 50 passes per day

Table 2.1.1: Recommendations for the use of embedded tracks with different pavements, different daily load

due to vehicles (busses and lorries)

The measurements of the test-bodies (length, breadth, height) are determined by the dimension of the test

circuit machine. To make the test bodies realistically, the at most possible measurements were chosen for

this. An approach towards the actual solutions in the streets only an approximation is possible. This

concerns particularly all embedded track types, which require a special compression or a special

installation on the spot. For example all tracks are included with an asphalt surface or nature paving

stones. Test bodies, which have to be produced from concrete, are almost unproblematic.

The number of test bodies to be examined with a series of experiments is limited on 16. Eight differently

embedded tracks should be examined in the context of the project "URBAN TRACK". To be able to

compare the results with each other, they had to be exposed to the same loads due to the wheels. This

means that the rails had to be installed identically into the test bodies. They should be rolled over

lengthways and crossways. On the spot the tracks are mainly run over in lengthways and crossways

direction, too. This situation was simulated by the arrangement of the rails in the test bodies.



Further influences how they exist in switches e.g. (spandrel in the common crossing) and by the

installation of gauge tiebars on the spot could not be taken into account till now at the tests carried out.

Special test bodies have to be made and subjected to a fatigue test at the circuit machine. This was not

possible in the context of the ongoing project "URBAN TRACK".

The recommendations summarized in Table 2.1.1 can therefore only be transferred to such cases, which

were simulated by the used test bodies. Cases of damage taken locally prove that the failure modes

appeared at the tests show the reality largely. This covers the realism of the circuit machine for fatigue

tests of tracks embedded in streets.

Summarizing it is to point out that only statements are permitted with respect to the boundary conditions

available at the tests (construction of the test bodies, load due to the rubber tyre, temperatures etc.). The

recommendations contained in Table 2.1.1 have to be understood only on this background. At present, a

generalization on all possible other application cases is not possible.

If more detailed statements are required, e.g. influence of gauge tiebars or switches, corresponding test

bodies have to be made and subjected to fatigue tests at the circuit machine.

2.1.8.4. Conclusion

To determine the influence of the load on tracks embedded in road surfaces exerted by heavy goods

traffic (buses and lorries), eight different carriageway and track structures were tested on a test circuit.

Corresponding test-bodies were produced for this purpose. These were then ‘driven over’ at a speed of V

= 50 km/hr and axle load of Faxle = 100 kN.

The key carriageway types studied were:

asphalt (in two variants);

pavement (in three variants);

concrete (in three variants).

The test-bodies were rolled over in three temperature cycles at temperatures of -10°C, +10°C and +30°C

room temperature. Each cycle comprised approximately 330,000 wheel crossings (a total of

approximately 1 million wheel crossings). This simulated a real load of over 10 years.

Other than the pavement structure with elastic joint sealing compound, all other test-bodies withstood

the load.

The measurements of the static vertical and horizontal stiffnesses found clear differences between

individual test-bodies. Subsequent checks in this respect revealed hardly any differences.

The surfaces of the individual test-bodies were ‘deformed’ in various ways by the wheel crossings. Most

significantly affected was the unbound pavement, followed by the asphalt base courses. By contrast, after

the tests the concrete bodies remained largely unaffected.

In summary, the tests found that all test-bodies with a concrete structure up to the surface (which also

includes a natural-pavement structure with concrete backfilling) withstood the tests well. This structure

is to be recommended for heavy loads (buses and lorries).



The green tracks studied and which must be suitable to allow emergency-vehicle access, yielded different

results. These tests were performed with a lower axle load, at slower speed and for a shorter test duration

(V = 30 km/hr and axle load of Faxle = 70 kN).

The solutions incorporating artificial grass on a solid concrete body withstood the loads without

sustaining any significant damage. By contrast, during the first part of the test the test-bodies designed

for planting with sedum failed when subjected to a load for only a short period. The two test-bodies with

a strip of drainage concrete approximately 10 cm wide alongside the rail withstood the loads for the

longest period but ultimately these, too, failed. After swapping the drainage layer material for drainable

base layer material in two test bodies (drain concrete version), and compression of the layer these two test

bodies withstood the remaining test (4,600 wheel crossings) without any damage.



2.2. OPTIMAL MAINTENANCE METHODOLOGY (WP2.2)

The work package WP2.2, on optimal maintenance methodology, is made of three work packages:

Visual inspection & maintenance (Proposal for a harmonised inspection and maintenance standard):

WP2.2.1, developed by FCP.

Predictive and preventive maintenance of metro tracks: WP2.2.2, developed by INSA, INRETS and

D2S.

Preventive maintenance of embedded tram tracks (Rail wear in curves and special track work for

trams): WP2.2.3.

2.2.1. Visual inspection & maintenance (WP2.2.1, developed by FCP)

2.2.1.1. Introduction

The objective of the work package “Visual inspection & maintenance” was to create a comprehensive

preliminary draft specification for urban railway tracks of public transport such as tram and metro. The

draft specification was created with an emphasis on visual inspection and is applicable for all urban

traffic network operators. The specification was aimed in particular at the small and medium size urban

traffic network operators.

2.2.1.2. Strategy used and description of the methods

The draft specification was created using a step by step methodology. External experts from universities

and operators assisted in compiling a preliminary draft specification. This draft specification formed the

basis for the discussions with the operators and the consensus finding process. The proposal document

and a questionnaire were distributed to several operators Urban Track members and other experts to

ascertain their views and opinions. Unfortunately the number of responses collected was very limited

and therefore the strategy was altered. Subsequently it was decided to identify and contact relevant

European operators and experts in the fields of inspection and maintenance to submit to them the draft

specification. In addition, independent personal meetings were organised which provided a forum were

relevant information, comments and remarks were collated through personal discussion.

2.2.1.3. Results

The final step of the intended consensus finding process was a short survey with three questions:

if the expert comments represent the official position of the represented operator,

if the operator is interested in a European standard for inspection and maintenance and

if the operator would support the standardisation work.

Results collected in interviews with relevant European operators are submitted in the Table 2.2.1 below.



Town Operator addressMetro

TramDate of visit Proposal of the Standard visual inspection & maintenance

Opinion/remarks are

representing for the

companies opinion

Standard would of value for

the company; Operator's

interest in existing the EU

Standard denoted as: absolute

("in fever"), interested,

perhaps, not interested,

strong opposite

Interest in the

future support of

work on Standard

1 ViennaWiener Linien GmbH & Co KGErdbergstraße 202, A- 1030

Wien

M+T several

"Wiener Linien" supported the creation of the proposal. The comprehensive Viennese Metro and

tramway in-house standard was provided as helpful background. Nevertheless the staff of “Wiener

Linien “ is of opinion that one-sided definition of limit values for urban track inspection and

maintenance is not currently purposeful because of the current rapid change of European knowledge

base in defining the rules and standards.The present research has shown that one-sided limit values

could be meaningful only if they would be given for particular track in particular urban conditions.

Technical expertise of the

expert

The interest in defining the

integral Standard for urban

tracks is not conceived at the

moment.

They are interested

to participate in the

future

standardisationprocess and give

their contribution in

domain of creating

mechanisms and

criteria for the future

2 Graz

GVB Grazer Verkehrsbetriebe

Grazer Stadtwerke AG

Verkehrsbetriebe, Technische

Services FAHRWEG,

Steyrergasse 116/II/Zi.208, A-

8010 Graz, Austria

T 26.03.2008

The operating staff in Graz is not be willing to deal with Standards in English language. Therefore no

direct remarks about the proposal are available. Nevertheless the wear limits of the tramway in Graz

have been provided and will be taken into accout.

State of the company

Not interested because the

operator is not able to deal with

the document in English

3 Dresden

DVB Dresdner

Verkehrsbetriebe AG,

Hohenthalplatz 7, 01067

Dresden, Postfach 100955,

01079 Dresden

T 04.06.2008Dresden advised that the recommendations in the standard proposal are useful for operators with wide

experience of maintenance. For new operators, these recommandations should be taken with caution.Yes

If a long experience in business

is available, standard must

reflect this and should not

inconsistent to the experience;

then acceptable

open

4 KarlsruheVBK Verkehrsbetriebe

KarlsruheT 30.03.2008 Involved in the consensus finding process Yes





then acceptable

open

5 Bremenbsag Brehmer StraßenbahnAG

T 05.06.2008 Involved in the consensus finding process Yes





then acceptable

open

6 Brussels

STIB Société des

Transports Intercommunaux

de Bruxelles

Avenue de la Toison d'Or, 15

1050 Brussels

Rue de Stassart, 36

M+T

Operator is of opinion that the proposal is a good guideline for urban railways. It comprises: many

aspects such as: geometry, construction, inspection, preventive and corrective maintenance as well as

measures that should be implemented in inspection&maintenance policy. They support work in

creating the EU Standard.

Opinion of the technical

expert of the companyInterested Yes

7 Paris

RATP Régie autonome des

transports Parisiens

Département EST - Unité I2E-

PTEC/VOIE

LAC VE01

56, rue Roger Salengro

94724 Fontenay-sous-Bois

Cedex

M+T 12.03.2008

The proposal of the Standard is not quite convenient to Paris track conditions. For example some

metro lines are running on rubber tyres. Therefore RATP prefers using the EN 13484 modified to the

metro conditions of Paris.


Proposed standards are not

convenient to metro conditions in

Paris, therefore there is no high

interest in implementation and

participation in standardisation

process.

Perhaps

8 StrasbourgCompagnie des TransportsStrasbourgeois - CTS

T The remarks have not been sent until now. Interested open

9 Porto

Metro do Porto, SA Avenida

FerànoMagalhàes, 1862, 7°

4350.158 Porto, Portugal

M+T15/16.09.200

8

Porto operator analyised the proposal in detail and gave remarks refered to intervention and alert limits

and enclosed the table with current implemented tolerances in Porto metro company. It should be

specified to which speed is the proposal based on, tolerances should be given for concrete and ballast

track separately. Some terminology in the proposal has to be more clarified.

Technical expertise of

experts' team for metro

maintenance&inspection

Interested but since they already

established many supporting

documents and the standard

does not fit fully to a major part

of the network, it would be not of

a great value for the company

Yes, occasionally

10 Barcelona

TMB Transport metropolitans

de Barcelona Av. Del

Metro s/n 08902 L'Hospitalet

de Llobregat

M+T 09.06.2008

A few remarks about the Standard were given: There was the wish for new geometric measurement

methods and devices for the inspection of levelling and horizontal alignment. The absolute coordinates

of the track are not such important and mostly unknown. Therefore it is senseless to compare existing

and projected coordinates. Relative measurements should be prefered in urban tracks with correlation

of lateral and vertical derivations (limits).

State of the company Interested Yes

11 Madrid

Metro de Madrid

Dr. Esquerdo, 138. 28007

Madrid

Cavanilles, 58. 28007 Madrid

M(+T) 15.02.2007

There was no proposal available at the time of Madrid visit but the document was sent afterwards. The

operator is of opninion that the Standard icould be of a great value for the company and therefore is

interested to be involved in the further work on Standard.

Technical expertise Absolute Yes

12 Birningham

Centro Midland Metro

Birmingham

Centro House, 16 Summer

Lane, Birningham, B19 3SD

M+?28.04.2008

Cologne

Technical remarks were given. Some terminology has to be clarified. A hardcopy of the proposed

standard with the remarks drawn in was delivered.State of the company Interested Yes

13 London London Trams M+T 27.01.2009 Questionnaire handed over personlly in January 09Andy Steel is the technical

resp. EngineerInterested Yes

14 NaplesMetronapoli

Via Ponte dei Francesi, 37/d -

80146 Napoli

M+T05/06.05.200

8

The operator agreed with the content of the Standard proposal. The special intention should be paid to

implementtaion of lubricant method according to opinion of metro staff in Naples. The second

important issue is ultrasonic inspection for welded rail joints as a measure for reducing the risk of railcracks and fractures.


Perhaps. At the moment their

interest is focused on the

standard impact on maintenancecost reduction

Yes, especially if

they would be

involved in site tests

15 Bergen bybanen, NSB lokaltog T 28.04.2008 The remarks have not been sent until now. (inspite of several reminders)Tom Potter is the technical

resp. EngineerInterested Yes

16 Helsinki YTV M+T 26.01.2009 The remarks have not been sent until now.

Yes, technical responsible

staff will be involved in the

answers

Open Open

17 Budapest

BKV Budapesti Transport

1146 Budapest, Hungária

krt.46

T 17.04.2008

A lot of information about weakness of the old track system, it's improvement and renewal as well as

the advantages of the new one have been presented in detail. The table with limits values

implemented in maintenance and inspection policy in Budapest transport company is given.

18 Warsaw

Tramwaje Warszawskie

01-424 Warzawa, al. Prymasa

Tysiaclecia 102, Poland

T 16.05.2008

The main part of tram lines in Warsaw is track with segregated right of way. According to problem

generated by noise and vibration, since 2000 the new strategy and method are in implementation in

operating the rail system. To reduce the noise effects an anchored system adopted from Germany is

used. In spite the efforts of operator staff in Warsaw remarks about the Proposal have not been

submited.

Technical expertise of

experts team for tram track

maintenance

Absolute Yes

19 Prague

DPP Dopravní podnik hl. M.

Prahy, akciová spolecnost,

Sokolovská 217/42, 190 22

Praha 9

M+T

28.04.2008

Cologne

12.06.2008

Praha

There are some remarks about measurements of horizontal alignment. The Czech operators (refer to

Brno operator too) are not involved in the creation of national standards. They want to avoid tougher

regulations of their ministry due to new European standards.


"Not interested" at the moment,

but being aware of importance of

standardisation process.

Implementation of

maintenance&inspection policy

in the future should be based on

the integral EU Standard

Existence of the

integral EU Standard

could be useful in the

future

maintennace&inspec

tion policy of

European countries

20 BrnoDopravní podnik města Brna,

a. sT 13.05.2008

The operator in Brno uses the national standards for tram operating system. Therefore their

collaboration in project was done in domain of information about track system types as well as in

inspection and maintenance policy carried out within the company. However the Brno operator is ready

and interested to collaborate in standardisation of maintenance and inspection policy for European

track systems.

Opinion of the technical

expert of the company

The operator generally support

the cretion of the Proposal. It

could be of value for the

operators' companies

They are interested

to participate in the

future

standardisation

process.

intergrated in the projectintergrated in the network of operator

not intergrated but intrerest

Table 2.2.1: Operator Interviews

An example of the effect of the use of the standard on life cycle costs (LCC) is given in the report. It

describes the approach of the LCC-calculation for the SP 2.2.1 “Visual inspection and maintenance”.



This case compares two maintenance variants based on the maintenance categories defined in the

“Proposal of European Standard for Track Inspection and Maintenance”. Table 2.2.2 shows the different

maintenance measures which are assigned to the categories.

Element Failure / Reason Measure How often /indication Classification *)

rail curve of small radius lubrication - fixed

station

continuous comfort/

environment

wheel squeal lubrication - fixedstation

continuous comfort/

environment

corrugated rail, burrformation

grinding, deburring ofrail and rail joint

after visualinspection;exceeding limits

for track gauge

cost-effectiveness

rail breakage applying joint bars;speed reduction orservice break ifnecessary until railbreakage can be

repaired

after visualinspection;feedback from

driver

safety

track gauge gauge narrowing grinding, deburring ofrail and rail joint

reaching safetylimit

safety

reachingintervention

limit

cost-effectiveness

reaching alertlimit

comfort/

environment

gauge widening build-up welding or

replacing rail

reaching safety

limit

safety

reachingintervention

limit

cost-effectiveness

reaching alertlimit

comfort/

environment

turnout preventivemaintenance

mobile lubrication after cleaning cost-effectiveness

preventivemaintenance

cleaning andlubrication of pointmechanism

before and afterwinter

cost-effectiveness

turnout &crossing

corrugated rail, burrformation

grinding, deburring ofrail

after visualinspection;feedback from

driver

cost-effectiveness



Element Failure / Reason Measure How often /indication Classification *)

ballast bed

sufficient resistance tolongitudinal andlateral creep is not

guaranteed

tamping after visualinspection

cost-effectiveness

contamination screening of ballast after visualinspectionand/orfeedback fromdriver

cost-effectiveness

sleepers breakage replace after visualinspection

safety

drainage failure cleaning, renewal in case of failure safety

planting

vegetation onthe tracks

mowing, weed-killing after visualinspection

cost-effectiveness

pavement -asphalt

► cracks -single or netlike

► nicks and joints

► depressions and

bulges

► lane grooves

► asset erosion

► lack of adhesion

removal and relaying after visualinspection

cost-effectiveness

pavement -paving

► tilted or protruding paving

stones

► depressions

removal and relayingor replacement by

asphalt

after visualinspection

cost-effectiveness

pavement –

concrete slabs

► tilting slabs

► sink, shift or brake

of slabs

► loose slabs because

of defect bedding

► protruding steel

edges

removal and relayingor temporary

replacement by asphalt

after visualinspection

cost-effectiveness

Table 2.2.2: Review of the different maintenance measures

2.2.1.4. Conclusions

The information gathered from operators varied greatly from only general statements to very detailed

comments. Discussions were sometimes difficult as the operator personnel undertaking the inspection

and maintenance work typically was not accustomed to working with English language documents.



Through the course of these discussions further aspects have been identified that have made the

definition of a uniform standard for track inspection and maintenance very difficult:

Confidentiality of “in-house procedures” for inspection and maintenance,

urban operators, which often belong to the local community are conscious of safeguarding regional

jobs and are reluctant to support the global companies,

for global working component suppliers the market is small, diverse, competitive and not significant,

apprehensiveness of operators towards European harmonisation and standardisation,

for large operators, with vast in-house expertise and sophisticated regulations and procedures

concerning the track – rolling stock interaction, a harmonised standard would be either irrelevant or a

step backwards.

The result of the survey to the operators showed only moderate interest to the standardisation and rather

opposition within significant operators.

In conclusion the working process for the proposal of the standard showed the diversity of urban track

systems, maintenance strategies, legal form of the company, opinions of operators and their preferences.

A standardisation is not recommended, however the document could be helpful as voluntary guidelines

for operators creating their own “in-house procedure”.

2.2.1.5. Bibliography

[1] Girnau G., Krüger F. (2007), Local and regional railway tracks in Germany, Verband Deutscher

Verkehrsunternehmen (VDV) (Hrsg.), Alba Fachverlag, Düsseldorf

[2] EN 13848-1 Railway applications/Track – Track geometry quality, Part 1: Characterisation of track

geometry

[3] Wu H., Shu X., Wilson N. (2005), “Flange Climb Derailment Criteria and Wheel/Rail Profile

Management and Maintenance Guidelines for Transit Operations, TCRP Report 71 (Volume 5),

Washington, D.C.

[4] Grassie Stuart L. (1995), Measurement of railhead longitudinal profiles: a comparison of different

techniques, Wear 191, p. 245-251, Elsevier Science S.A.

[5] TCRP Report 71, Flange Climb Derailment Criteria and Wheel/Rail Profile Management and

Maintenance Guidelines for Transit Operations (USA)

[6] Naue M. (2003), Messmethoden zur Bestimmung von Verschleiss und Lagegenauigkeit von

Straßenbahnschienen, Diplomarbeit, Universität Fridericana Karlsruhe, Institut für Straßen- und

Eisenbahnwesen, Karlsruhe

[7] http://railmeasurement.com/cat.htm

[8] Grassie Stuart L., Edwards J., Shepherd J. (2007), Roaring Rails – an enigma largely explained,

International Railway Journal, July 2007, p. 31-33



[9] EN 13848-5 Railway applications/Track – Track geometry quality, Part 5: Geometric quality

assessment

[10] APTA RT-S-FS-002-02, Standard for Rail Transit Track Inspection and Maintenance, Authorized

September 22, 2002

[11] EN 13674-1 Bahnanwendungen - Oberbau - Schienen - Teil 1: Vignolschienen ab 46 kg/m

2.2.2. Predictive and preventive maintenance of metro tracks (WP2.2.2, developed by INSA,

INRETS and D2S)

This chapter deals with “predictive and preventive maintenance of metro tracks”. Its objectives are to

develop optimized inspection methods and maintenance procedures guided by a low cost efficient

monitoring system and taking into account LCC aspects.

At the beginning of the project, during a meeting in London (SP2 meeting, 11/2006), it was decided to

split the topic in several parts:

first a more theoretical study (WP2.2.2a), especially of interest to the larger metro networks,

developed both by INSA for a better understanding of rail lubrication impact, and by INRETS to

solve the problem of rail track reliability estimation, and

second a direct application study, the Manila case (WP2.2.2b), providing low cost solutions in a short

term, especially of interest to the smaller metro and LRT networks.

2.2.2.1. Understanding rail lubrication impact (WP2.2.2a, developed by INSA)

This part of the study is very specific: INSA work as part of WP2.2.2.a was to investigate rail lubrication

in the aim of optimizing the frequency of maintenance operations while minimizing friction and wear as

a function of the contact’s geometry, contact conditions, mixture rheology. The term mixture will be

commonly used in INSA work. The mixture is composed of a mixing of detached metallic particles (from

wheels and rail), mineral particles (sand) and lubrication oil.

Figure 2.2.1 Mixture between rail and wheel

Mixture (3rd body)

Contact geometry

Lubrication:"initial"

[oil + asphalt]

Detached particles

Wear flow



It is the first time that the mixture present at the interface between the wheel and the rail has been taken

into account and its rheology been characterised, on the basis of the analysis of a RATP example. The

tribological approach developed for the RATP network could be transposed to others networks involved

in the project.

The rheology tests were performed on a Bridgman simulator (used in this case as a “rheometer”).

Observations of the anvils surfaces were performed after tests with optical microscope. They highlighted,

whether the mixture is dried or not:

oil bleeding from the mixture and the trapping of the additives of oil in the roughness of the anvil;

“selective” ejection of parts of the mixture out of the contact surface.

The additives trapping highlights chemical reaction of additives with surfaces anvils. The torque has

been registered during the tests and highlights that probably the oil-bleeding modifies the limit

conditions – friction coefficient - of the contact. The amount of the ejected mixture or parts of the

mixture out of the contact is higher in the case of the fatty initial mixture compared to the dried one. This

can be due to a different initial amount which is difficult to control.

The chemical reactions of the oil and/or asphalt and/or additives of oil with fresh surfaces of the

detached particles – highly reactive – can also effect on the oil bleeding and the ejection of mixture.

Conclusions

A good lubrication process reduces the wear and the friction in the wheel flange and flange root,

meanwhile keeps the rail head dry for optimal adhesion (traction and breaking). Whereas in urban rail

networks, wheel rail lubrication in narrow curves is an important topic in terms of maintenance cost, life

time and security very few research investigations have been done on this complex problem. As a

consequence this work performed by INSA on rail lubrication was exploratory.

The research has been divided in four main parts:

First INSA meets lubrication experts for the wheel-rail contact to understand how the process

adjustment and the maintenance are done on RATP network1 (the tribological approach developed

from RATP network study could be transposed to others networks).

Secondly the tribological properties of the mixture are characterised. To do this, sampling is done on

RATP network.

Thirdly the test benches used are described, and then the formation and the tribological behaviour of

the “wear” mixture (initial lubricant + wear particles) investigated.

Fourthly a numerical model will be settled to access to local wheel-rail contact characteristics (i.e.

contact geometry evolution during traffic, contact positions on the rail surface, contact pressures,

1 RATP network has been chosen at the beginning of the project for a first investigation, especially to reduce

travel costs.



plastic deformation… ) under various lateral loading conditions from straight track to sharp curved

track.

Setting on an on-site experimental feedback, RATP has found for one initial lubricant the way to form in

situ an efficient mixture. Best practice has defined a “good lubrication” state, and the maintenance policy

in term of lubrication is to maintain this state of lubrication. From our own experience, previous work

highlighted the same state on others networks (SNCF for example), that’s why this “good lubrication

state” was chosen as reference case. It is now obvious that a good lubrication required the formation in

situ of a mixture. This mixture is the melting of the initial lubricant and the particles detached from the

wheels and rails. Thus the study focused on the tribological study of the mixture.

The chemical composition and the texture of this mixture have been investigated with different specific

tools: Photonic Microscope, Environmental Scanning Electronic Microscopy (SEM) and X-ray energy

dispersive analysis (EDX).

The mixture rheology has been studied on a Bridgman simulator which allows reproducing contact

pressure and high shearing conditions. Different mixtures sampled on site have been tested and their

functioning analysed (range of friction coefficient from 0.005 to 0.015, localisation of the velocity

accommodation in the skin (interface) or in the bulk of the mixture).

A roller / plane simulator of INSA was modified in link to the wheel flange-rail active root flange contact

configuration. Then tests have been performed in the aim:

to investigate and to begin to understand the formation of the mixture and its tribological

functioning. Special attention was given to its life time (maintenance) and the friction coefficient

value (security, derailment and wear),

to get a representative and useful tribological tool, enabling to validate new lubricants and new rail

profiles under realistic contact conditions.

As the reality is complex, it is necessary to draw a parallel between the results of the laboratory tests and

the results obtained by expertises of samples issued from real site. This approach allows validating the

laboratory results.

From the experimental investigations, a tribological scenario of the functioning of the mixture leading to

a low friction coefficient (efficient mixture, 0.05<µ<0.01) can be proposed (figure 2.2.2). Once this mixture

is formed, its rheology allows to fill in the local roughness of the rail (from µm to tenth of µm) and thus a

smooth surface is created ; this last allows the velocity accommodation to be activated in a very thin

superficial layer (nm) composed by the initial lubricant additives adsorbed on this smooth surface

(surface complex). The initial lubricant is itself brought on this surface by bleeding caused by the high

contact pressure (and perhaps by shearing). The different values of friction between mixtures can be

explained by the localization of the velocity accommodation: in the extreme surface of the mixture (skin)

or in the bulk of the mixture.



Figure 2.2.2: A tribological scenario

The control of the lubrication process requires the control of the initial formation of an efficient mixture

and its holding in the contact, which means a specific optimized rheology of the mixture, a localization of

the velocity accommodation (surface) with a low friction. Its formation can be in situ or ex situ. Given the

state of current knowledge, it does not appear possible to formulate a product (ex situ) whose rheology is

similar to that of the mixture and which can be deposited on the active flange of the rail surface.

Consequently, it is necessary to orient efforts towards the use of controlled rail-wheel wear to obtain the

“right” mixture. Its formation has to be in situ. Thus the two phenomena, leading to the formation of this

efficient mixture, have to be investigated:

the detachment of particles,

the physico-chemical reactivity of the particles with the initial lubricant (oil + additives) under

tribological stresses (pressure, shear).

The mechanisms of the lubrication of the active rail gauge involve complex coupling phenomena, which

do not allow elementary parametric studies on site (in practice, the parameters involved are never

modified one by one). As for a consequence, a laboratory test developed in this study will allow to finish

the understanding and then to investigate new biodegradable (for example) lubricants. Note that the

validation of a new lubricant is in progress. This new tribological tool enables to preset new lubricants

under realistic contact conditions in laboratory, before to perform qualifying tests on industrial test bench

or on site.

The numerical modeling proposed in parallel of the experimental simulations allows investigating the

local effects of the local friction and of the contact geometry (i.e. new, worn…) on the local stresses fields

and thus on the detachment of particles. Last, but not least, further work should integrate:

the “right” behavior laws of the materials under stresses as those found under contact, i.e. high

hydrostatic pressure and high shear gradients,



the mixture, which could be taken into account thanks discrete elements modeling

Despite its high prospective level, this study brings experimental and numerical tools:

to finish the understanding of the lubricating mechanisms involved in the contact in curves, and thus

of the tribological functioning of the mixtures,

to specify more precisely criteria for quantification of the rail lubrication in the aim to control the

maintenance,

to formulate some new lubricants,

to understand the geometric effects of the wheel and the rail.



Effect of theprofiles

Active flange lubrication

RATP lub. cond. µ<0.02 µ<0.1

Effects of the oil additives

Smooth surface

Flows of the mixture

Reality Simulations

Experimental Numerical

Mixture Contact location

Geometry effect

Effect of µ

Location Pressure

“Patine“(specific surface aspect, i.e. the

good 3rd body to lubricate)7 trains, Extreme pressure oil

Qualitativevalidation

AN

AL

YS

ES

60 mm

1 mm

Semi quantitativevalidation

Sp

ec

if

ic

at

io

n

Life duration of the mixture

CPress (MPa)

750

20 50

Others networks

Profiles

Validation

Specification

Conditions of themixture formation

Representativetest

AdditivesLubricationconditions

Figure 2.2.3: Scenario of mechanical-chemical operation of the mixture



2.2.2.2. Solving the problem of rail track reliability estimation (WP2.2.2a, developed by

INRETS)

This part of the study is dealing with mathematical modelling as a support tool to help solving the

problem of rail track reliability estimation. Nowadays, reliability analysis has become an integral part of

system design and operating. This is especially true for systems performing critical applications.

Typically, the results of such analysis are given as inputs to a decision support tool in order to optimise

the maintenance operations. Unfortunately, in most of cases, the system state cannot be evaluated exactly.

Indeed, it is uncommon to be able to deterministically describe the process each component, part of a

complex system, reaches a failure state. This is one of the reasons which have led to the important

development of probabilistic methods in reliability.

The aim of this sub-project is to develop a virtual maintenance tool that is able to model and integrate the

track degradations in relation to inspection and maintenance rules. This tool, called “Graphical Duration

Model”, DGM, - see below - will be implemented in order to take into account the random behaviour of

degradation processes. Partners RATP and INRETS have experience with these methods. This kind of

mathematical tool can unwind the life cycle of a specific component and carry out its interaction with the

maintenance operations in accordance with a given strategy. So, optimised maintenance rules can be

highlighted for given exploitation conditions. One can thus quantitatively evaluate predictive or

opportunist maintenance strategies versus curative ones, in terms of financial costs as well as safety or

availability costs.

This chapter presents the results obtained during the first year of the project. First, the theoretical frame

of the study (PGMs and DPGMs theory and some details about the parameters learning) is introduced.

Then is explained how to model the reliability of complex systems using a proposed graphical approach.

Finally, some conclusions and perspectives are discussed.

BACKGROUND

A wide range of works about reliability analysis is available in the literature. For instance in numerous

applications, the aim is to model a multi-states system and therefore to capture how the system state

changes over time. This problematic can be partially solved using dynamic modelling (i.e. Markov

framework) [1]. The major drawback of this approach comes from the constraint on state sojourn times

which are necessarily exponentially distributed. This issue can be overcome by the use of semi-Markov

models [14] which allow considering any kind of sojourn time distributions. On the other hand, one can

be interested in modelling the context impacting on the system degradation [11]. A classic manner to

address such an issue consists in using a Cox model [6] or a more general proportional hazard model

[12]. Nevertheless, as far as we know, it is unusual to find works considering both approaches at the same

time.

Moreover, recent works in reliability involving the use of Probabilistic Graphical Models (PGMs), also

known as Bayesian Networks (BNs), have been proved relevant. For instance in [4], the authors show

how to model a complex system dependability by mean of PGMs. [13] explains how fault trees can be

represented by PGMs. Finally in [19], authors show how convenient Dynamic Graphical Models are in

order to study the reliability of a dynamic system represented by a Markov chain. Our work aims to

describe a general methodology to model the stochastic degradation process of a system, allowing any



kinds of state sojourn distributions along with an accurate context description. We achieve to meet these

objectives using a specific Dynamic Probabilistic Graphical Model (DPGM) called Graphical Duration

Model (DGM).

PROBABILISTICS GRAPHICAL MODELS

Definitions

Probabilistic Graphical Models (PGMs), also known as Bayesian Networks (BNs) [10], are mathematical

tools relying on the probability theory and the graph theory. They allow to qualitatively and

quantitatively representing uncertain knowledge. Basically, PGMs are used to describe in a compact way

the joint distribution of a set of random variables 1,..., NX X . Formally, a PGM, denoted by M, is defined

as a pair 1,

N

i iG p

, where:

G=(X, E) is a Directed Acyclic Graph (DAG). 1,..., NX X X is a set of nodes representing random

variables and E is a set of edges encoding the conditional independence relationship between the

variables in the model. Thus, G is a qualitative description of M.

1

Ni i

p

is a set of Conditional Probability Distribution Functions (CPDs) aiming to describe the

quantitative aspect of the model. It is worth noting that if the random variable Xi takes its values in a

finite and countable set Xi (e.g. 1,..., Ki i iX x x ), the CPD of Xi can be defined by a Conditional

Probability Table (CPT). On the other hand, if Xi is an infinite set then pi is a conditional density

function.

The underlying conditional independence assumptions introduced by this modelling allows to

economically rewriting the joint probability distribution:

where i denotes the subscripts of the ith variable parents in the graph. Thereby, it is important to remark

thati

X is no longer a single random variable but a set of random variables containing the parents of Xi

in the graph G.

CPD parameters learning

Both the qualitative and quantitative parts of a PGM can be automatically learnt [17] if some data or

experts’ opinions are available. The latter problem can be boiled down to probability distribution

estimation. We consider that the CPDs of the model are the 1i

N

ip

where θi represents the parameters of

the ith CPD. Thereby, the objective becomes to deduce estimates of 1

Ni i

using the available knowledge.

A classic manner to tackle this problem is to use the Maximum Likelihood (ML) method to exploit



information in databases. If some a priori information is also available (e.g. experts knowledge), one can

use bayesian methods [8] and compute Maximum A Posteriori (MAP) estimates of the parameters. To

that end, it is possible to use the factorisation property of PGMs, so that each θi can be locally estimated

using only the ith CPD.

Suppose that we have a database containing M observations of each variables Xi, denoted by , 1

M

i m mx

,

then the ML estimate of the ith CPD is compute by solving the following equation:

If some a priori knowledge is available about i, equation (3) becomes:

where is a function aiming to model the knowledge available on the parameter.

Inference in PGMs

Using PGMs is also particularly interesting because of the possibility to propagate knowledge through

the network. Various inference algorithms can be used to compute marginal probabilities when the

model becomes more complex. Inference in PGMs [9] allows taking into account any variable

observations (also called evidence) so as to update the marginal distribution of the other variables.

Without any evidence, the computation is based on a priori distributions. When evidence is given, this

knowledge is integrated into the network and all the marginal distributions are updated accordingly.

Finally, it is important to notice that such a modelling is unable to model the dynamic of a non stationary

system. For instance, in reliability analysis, one can be interested in modelling how a system changes

from an "up" state to a "down" state over time. For this kind of problem a possible solution consists in

using the dynamic extension of PGMs which are presented in the next section.

DYNAMIC PROBABILISTIC GRAPHICAL MODELS

Dynamic Probabilistic Graphical Models (DPGMs), also known as Dynamic Bayesian Networks (DBNs)

are convenient tools to represent complex dynamic systems. The term "dynamic system" makes reference

to a system of which state can change over time but with a fixed structure. To that end, DPGMs allow

variables to have temporal (or sequential) dependencies.

Strictly speaking, a DPGM is a way to extend PGM to model probability distributions over a collection of

random variables 1, , *,...,t N t t

X X

. A DPGM MD is defined [16] to be a pair 1,M M where:

M1 is a PGM which defines the prior distribution 1,1 ,1,..., NP X X as in equation (1).

M is a s-slices Sequential Probabilistic Graphical Model (s-SPGM), also named s-slices Temporal

Bayes Net (s-TBN) in the literature. s makes reference to the temporal dependence order of the model.



In this paper, we will limit ourselves to the case of a 2-SPGM which mean that the present (slice t) is

only dependent on the one step past (slice t-1). It is worth noting that we would rather use the more

generic term "sequential" instead of "temporal". Indeed, in many applications (e.g. genetic or

reliability), the dynamic of the studied system does not necessarily rely on time (e.g. genetic

sequence, number of mechanical solicitations for device).

Basically, M is also a PGM used to define the transition model which describes the dependencies

between variables in slice t-1 and variables in slice t. It aims to specify the CPD

1, , 1, 1 , 1,..., ,...,t N t t N tP X X X X taking advantages of the factorization property in PGMs:

where ,i tX is a set of the parents of ,i tX which could contain variables in the slices t and t-1.

Note that the slice of M is identical to M1, the latter can be omitted and the DPGM is strictly equivalent

to a 2-SPGM.

Then, it is possible to deduce the distribution 1, , 1,...,

T

t N t tP X X

by "unrolling" the 2-SPGM until we

have a sequence of length T:

The fact that t is an integer means we only consider discrete stochastic processes. This restriction is not

very penalizing in survival analysis because the duration variable is often expressed as an integer (e.g.

number of hours, days, years, solicitations… before a failure).

The figure 2.2.4 shows how to represent a classic Markov chain subjected to two covariates with a DPGM.

This kind of simple model can be use in reliability to model the state of a system, Xt, given some

contextual variables, Z1 and Z2, over time.

Figure 2.2.4: A Markov chain with covariates represented by a DPGM.



Finally, as it is possible to consider a DPGM as a big unrolled PGM, it is clear DPGM inherits the

convenient properties of classic PGM. Indeed, learning methods do not change when using DPGM.

Concerning the inference problem, most of the methods are based on static PGM inference algorithms

[16].

INTRODUCTION OF THE GRAPHICAL DURATION MODELS

Recent works in reliability involving the use of PGMs have been proved relevant since they are

particularly suitable to model the dynamic of a complex system [4]. Nevertheless in the field of

reliability analysis and as far as we know, no author seems to have gone far the use of DPGM to

represent more complex models than a Markov process with exogenous constraints as in [19].

In this article, we propose to extend the variable duration model introduced in [16] to build a

comprehensive model for complex survival distributions.

Qualitative definition

The proposed model, which we denote by Graphical Duration Model (GDM), is depicted in figure 2.2.5

as a 2-SPGM. This model allows describing, in a flexible and accurate way the behaviour of a complex

system given its context. Indeed, three different parts are considered:

The system state (Xt) over the sequence.

The covariates 1, ,, ...,t P tZ Zused to describe the system context.

The duration variable D

tXdescribing how long the system remains in a specific state.

Moreover, a transition variable (Jt) is added to explicitly characterise when the system jumps into another

state. Indeed, if Jt=1, it means that the system state will change at time t+1. On the other hand, while Jt=0,

the system remains in the same state. This variable is not necessary but appears to be convenient for

further generalization and Conditional Probability Distributions (CPDs) definition. In addition for the

sake of readability, we denote by Zt the random variable vector 1, ,, ...,t P tZ Zand by zt an observation of Zt,

in other words 1, ,, ...,t t P tz z zwith zP,t an observation of the variable ZP,t .

Figure 2.2.5: Representation of a GDM.



Then, it is possible to factorise the joint probability distribution of the variables Xt, XtD, Jt, Z over a

sequence of length T as it follows

Besides, in this model the system state transition depends on the duration spent in the current system

state and the current state itself. Thus, we are in a discrete semi-markovian approach [2][3]. Indeed, we

can specify any kind of state sojourn time distribution by contrast with a classic markovian approach in

which all durations have to be exponentially distributed.

This modelling is particularly interesting since it allows taking into account complex degradation

distributions and context effects at the same time.

CPDs definition

The following paragraph addresses the specification of each CPD involved in equation (3)

characterising the joint probability distribution in a Graphical Duration Model (GDM).

Covariates PDFs

We suppose that each covariate Zp takes its values in the set p, so that Zt is defined over the set

Z=Z1x...xZP. As the covariates do not have any parent in the model, their Probability Distribution

Function (PDF) is not conditional and for each p we have:

For instance, suppose that we are studying a component which is considered to be only subjected to

its type of functioning speed ("slow", "normal", "fast"). In this case, there is only one covariate Z1. Its

PDF could be represented as a table (or vector) with three elements slow, normal and fast specifying

the different proportions of using types.

System state CPDs

We make the assumption that the number of system states is finite and let 1,..., KS s s be the set of

the K different states. The first CPD concerns the distribution of the initial system state according to

its context:

where )(zpX1is a vector of K elements depending on the vector of values z1.



The second state CPD concerns the dynamic transition from one state to another. As a transition

occurs at time t if and only if the variable Jt-1=1, we have

where A(zt) is a stochastic matrix of size KxK depending on the covariate values zt. In general, A(zt) is

named the transition matrix of the system.

On the other hand, if Jt-1=0, the system remains in the same state. Therefore, the CPD is deterministic

and the transition matrix has to be equal to identity:

Duration CPDs

The first duration CPD describes the sojourn time distribution for each state and each combination of

covariates. We denote byDX

pthis conditional duration distribution and we have:

where( , , )D tX

p d i zrepresents the probability to stay during d time units in the state si given the

context zt. Besides, as we are studying discrete-time models, the duration unit d is a non negative

integer.(.,., )D tX

p zcan be seen as an infinite matrix (along its first dimension) depending of covariates

values zt.

In practice, it is possible to set an upper time bound D so as the time scale becomes finite. Indeed in

this case, d{1, …, D} and(.,., )D tX

p zis a finite matrix of D x K elements.

The dynamic duration CPD aims to memorize the time spent in the current state. Indeed, if the

previous remaining duration is greater than one, we update the remaining time by deterministically

decreasing it by one unit.

If the previous remaining time reaches the value one, a transition occurs at time t and the duration in

the new current state is drawn according to the CPDDX

p. In other words,

Let us note that the case 1 1DtX and 1 1tJ is not consistent. As a consequence the previous CPD is

undefined for these values. We can illustrate the duration CPD in the case of two discrete covariates

and geometric duration distributions. Then,DX

pis a parametric CPDs defined for any (d, i, z1, z2) by



with θ (i, z1, z2) the geometric distribution parameters for each state si and each pair of covariate

values z1 and z2.

Finally, it is worth noting that the discrete-time assumption laid on duration distributions by the

modelling can be easily overcome. Indeed, authors in [5] present a survey of discrete lifetime

distributions and describe some of them which come from usual continuous ones (e.g. exponential,

Weibull).

Transition CPD

Jt is a random variable characterising the occurrence of a system state change at time t. More

precisely, when Jt=1, a transition is triggered at time t+1 and the state remains unchanged while Jt=0.

Besides, a transition occurs at time t+1 if and only if the remaining duration in the current state at

time t equals one. As a consequence, the CPD of variable Jt is deterministic and defined by

RELIABILITY ANALYSIS USING GDM

Basic definitions

In this section, we suppose that the set of system states S is partitioned into two sets U and D (i.e. S=UD

with UD=), respectively for "up" states and for "down" states (i.e. OK and failure situations). The

system transition matrix from equation (3) can be decomposed as follows:

The four sub-matrices introduced in the previous equation allow to specifically describing the transition

rates between up and down states. Typically, in a reliability study without maintenance action, it is

impossible to go back into an up state if the system reached a down state (except for self reparable

system). In this paper we assume that the matrix ., ,.D UA z is equal to zero.

Reliability

Let R: N* → [0,1] denote the reliability of the system. R(t) represents the probability that the system is

always stayed in an up state until moment t. In other words,

Similarly, let TD denote the random variable describing the first hitting time of the subset D, i.e.

*infD tT t X D and then the reliability is given by



Although the reliability is supposed to be undefined for t=0, we set that R(0)=1 by convention which is

useful for the definitions given in the sequel.

Finally, we can remark that in the case 0D UA z

(i.e. D is a set of absorbing states), we have

Failure rate

The failure rate h: N* → [0,1] is defined as the conditional probability that the failure of the system occurs

at the moment t given that it has worked until moment t-1. In other terms,

Besides, the failure rate can be expressed using the reliability as follows:

Mean Time To Failure (MTTF)

The Mean Time To Failure (MTTF) is defined as the expectation of the lifetime (i.e. the expectation of the

hitting time to "down" states D):

Once again, it is possible to express the MTTF with the reliability:

Conclusions

As the failure rate and the MTTF can be expressed using the reliability, the objective is to build an

algorithm able to compute R(t). The simplest approach consists in using a generic graphical model

inference method like those based on junction trees. Unfortunately, these kinds of methods are not

optimized for the problem of reliability estimation since they involve extra-calculations (e.g. junction tree

building, backward probability propagation) which are not necessary for our problematic. That is why in

the next section, we propose an efficient and simple algorithm aimed to estimate the probability of any

sequence of state subsets defined as }}, where each T S with S, the set of the system states.

Thus, by setting ,...,

t times

U U

, the method will provide R(t).

Besides, let us note that exact calculations can be carried out provided all the CPDs in the model are finite

and discrete (i.e. represented as CPTs). Otherwise, one can resort to use approximate inference algorithms

which allow in general working with any kind of CPDs.



ESTIMATION METHOD

By analogy with the Markov property, it is straightforward to verify that in a GDM, the pair ( , )Dt tX X d-

separates the future (slices t+1) from the past (slices t-1 1). In other words, the future is

independent from the past given ( , )Dt tX X which is noted:

As it is shown in the next paragraphs, this property is the key to make tractable calculations in GDMs.

The aim of the following paragraph is to build an algorithm able to compute the probability:

To begin, let 1 1 1 1( , ) ,..., , , Dt t t t ti d P X X X i X d , then using the DGM joint distribution

factorization, we obtain:

where z=(z1, …, zp). As a consequence, from the previous equation, we deduce the initial probability to

begin in the subset of states 1:

Besides, we can write:

Observing that marginalizing onto variables 1 11 1

, ,D

tZ X J

lets the term C1 unchanged and sums to

one the term C2, it follows:



Hence using this result, we can express t as a function of t-1 since we have:

In addition for the sake of readability, let ( , ', , )tm j d i d denote the quantity:

such that equation t(i,d) can be rewrite as follows:

Finally by definition of t, we find that:

To sum up, theses results show that given any state sequence={1, …, T}, the following forward

recursion allows to compute the probability of the sequence :

Some aspects about the behaviour of the previous recursion are discussed in the three following remarks:



Under the classic assumption according to which all the CPDs are identically distributed over time as

soon as t2, then mt does not change during the recursion. Thus, it is possible to compute mt once and for

all which decreases the algorithm computing time.

If all the CPDs are finite and discrete (i.e. represented as CPTs), then integrals over the Zp’s and infinite

sums over N* become finite sums which allows to perform exact calculations.

For instance, if we set 1 { ,..., }

t times

U U , and 2 1

1

{ ,..., , }

t times

S S

respectively, then the previous method will

compute R(t) and t tP X respectively.

APPLICATION TO TRACK RELIABILITY ESTIMATION

Nowadays, the increasing of traffic and axle loads has lead to a rail breaks growth. For safety reason,

restrictive exploitation rules were defined (a train can run on a breaking rail but only after an

enforcement process and with low speed) increasing delays and then, diminishing the service quality.

Moreover, expensive corrective maintenance costs are needed to make up for this kind of failure.

Therefore, efforts are being made for the application of reliability-based and risk-informed approaches to

maintenance optimisation of railway infrastructures. The underlying idea is to reduce the operation and

maintenance expenditures while still assuring high safety standards [18].

In this application, we will focus on the reliability analysis of the rail and let maintenance modelling for

further works.

Variables definition

Let define the meaning of the different variables involved in the GDM considering our railway case

study.

Z1,t represents the type of the material installed in the studied track section: "homogeneous rail" (R),

"welding" (W) and then Z1={R, W}.

When a serious damage is detected, maintenance operators proceed to a local rail renewal. To that end,

they perform an aluminothermic welding which leads to two welding joints on the rail section tips. As

the welding lifetime is lower than the rail lifetime, most of new damages occur around the formers. As a

consequence, the more welding are installed, the weaker the global reliability of the studied track is.

Xt is the state of our system, namely the studied rail track between two stations (in our application we

consider the inter station “Gare de Lyon-Nation”). We consider three states of degradation: "no defect"

(N), "minor defect" (D), "critical failure" (F) and then S={N, D, F}.

The first two states do not bring on service disturbances or safety problems like the last one. That is why

we set U={N, D} and D={F}.

XtD is the duration variable. In this case, we set the duration unit to be the month.

As all the variables take finite and discrete values, it is possible to use an exact inference algorithm to

compute the track reliability and related metrics over time.



CPDs learning

Feedback experience databases are used to estimate the CPDs parameters using the statistical method

presented in equation (2).

Table 1 gives an extract of the database used as input of the learning process. Each entry of this database

represents a change of the considered track state. For each change (i.e. each entry), the following

information are available:

The context at which the change occurs. In this example, only the singular point (rail/welding) is

considered.

The state of the track before the change (state t).

The duration spent in the state before the change.

The new state after the change.

For instance, the first entry shows that a welding (W) part of the considered track is stayed 23 months

without any defect (N) until a minor defect (D) appeared. The last entry illustrates the case of a critical

failure (F) occurring on a rail which spent 77 months in a healthy state (N).

From these feedback experience observations, the two main groups of parameters (i.e. the transition

tables and the duration distributions) will be estimated.

Singular point State t Duration (month) State t+1

W N 23 D

W D 1 F

W N 10 F

R N 77 F

Table 2.2.3: Exploitation of feedback experience databases

Learning results concerning the duration CPDs are depicted in figure 2?2.6. These histograms represent

for each singular point, the probability to stay a certain duration given the system is entered in a certain

state. For instance, let consider a rail which has just jumped in the healthy state (e.g. after a renewal), then

the upper left subfigure shows that the considered rail has a high probability to stay between 20 and 40

months before a change. On the other hand, the upper right subfigure considers the case of a welding of

which the duration before a change has a high probability to value between 5 and 20 months.

Consequently, these results allow quantifying the well-known fact that a welding is less resistant than a

rail.



Figure 2.2.6: Histograms representing the duration CPDFs for state N.

Tables 2.2.4 give the learning results for the transition tables of the system according to its context

(rail/welding). Therefore, each table sets out the probabilities that the system goes to a certain state from

an initial state during a change given a specific context. For example, in the case of a welding, the right

sub-table indicates that the system goes directly in a critical failure state (F) 68% of time whereas the

system transits through a degraded state (D) 32% of time.

We can note that from a “healthy state” it is more probable to reach directly a critical failure without

having detected a minor defect.

Indeed, this phenomenon makes difficult the application of preventive maintenance policies since

preventive decisions are usually taken when the defect is still minor.

Table 2.2.4: System transition CPTs N (i.e. A(.,.)).

In the next section, we present some results obtained when combining all the knowledge contained in the

local CPDs in order to compute the considered track reliability.

Results

The model developed and applied during this first year has been implemented in MATLAB®

environment, completed by the free Bayes Net Toolbox (BNT) written by Kevin Murphy [15]. Exact

inference algorithm [8] has been used to compute reliability since all the CPDs can be represented on



table (see figure 2.2.7(a)). Then, failure rate and MTTF have been deduced based on reliability estimations

and depicted in figures 2.2.7 (b) and 2.2.7(c) respectively.

These figures allow characterising the behaviour of the studied system. As a consequence, useful

information can be deduced from such analysis in order to set up and optimize reliability-based

maintenance policies.

Figure 2.2.7: (a) Reliability as a function of the welding rate.

CONCLUSIONS AND PERSPECTIVES

The WP2.2.2.a aims at reducing the unavailability of tracks, setting up an optimal predictive maintenance

strategy. It is therefore necessary to determine the optimum cycles of intervention to reduce the costs of

the maintenance. For that purpose, the Diagnostic and Maintenance team from LTN INRETS laboratory

uses to develop maintenance simulation tools based on the knowledge of the degradation processes of

the component.

The chosen application concerns the rail maintenance of RATP RER tracks.

Figure 2.2.7 (b) Failure rate as a function of the welding

proportion.Figure 2.2.7 (c) MTTF as a function of the welding rate.



The task was divided in three main phases: the modelling of the process of degradation of the rail, the

modelling of the maintenance and, finally, the optimization of maintenance policies.

Within the first twelve months of the project, the process of rail degradation was modelled by an original

probabilistic graphical approach (i.e. bayesian networks). The proposed method based on the GDMs aims

to study the behaviour of any complex system. Our approach turns to be a satisfying and a

comprehensive solution to model and estimate reliability. Indeed, the proposed modelling is generic

since it is possible to take into account the context of the system along with an accurate description of its

survival distribution. So, even if all results are introduced in a RATP context, the extension of our

approach to whatever kinds of urban tracks can be easily done, since all knowledge describing the track

is available.

In addition, as the method is based on graphical models, it makes it more intuitive and readable than

more theoretical models.

The encouraging results obtained in this first year of the Urban Track project confirm that GDMs are

competitive reliability analysis tools for practical problems. Nevertheless, results introduced in this report

are limited to the rail maintenance of one specific inter station. But, it is extendable to any other track,

other component… provided feedback experience data are available for the system we want to analyse.

Next step will address the problem of maintenance modelling, with the aim to build different reliability-

based maintenance models which rely on GDMs. Later on, focus will be put on the development of

optimisation method in order to determine optimal maintenance policies. Then, the final tool could be

used as help to decisions by the people in charge of the maintenance of the track to evaluate the economic

performance of the new cycles of various maintenance operations with respect of safety considerations.

(a) References

[1] T. Aven and U. Jensen. Stochastic Models in reliability. Number 41 in Stochastic Modelling and

Applied Probability. Springer, 1999.

[2] V. Barbu, M. Boussemart, and N. Limnios. Discrete time semi-markov processes for reliability

and survival analysis. Communication in Statistics - Theory and Methods, 33(11):2833–2868, 2004.

[3] V. Barbu and N. Limnios. Nonparametric estimation for discrete time semi-markov processes

with applications in reliability. Journal of Nonparametric Statistics, to appear.

[4] H. Boudali and J. B. Dugan. A discrete-time bayesian network reliability modeling and analysis

framework. Reliability Engineering & System Safety, 87(3):337–349, March 2005.

[5] C. Bracquemond and O. Gaudoin. A survey on discrete lifetime distributions. International Journal

on Reliability, Quality, and Safety Engineering, 10(1):69–98, 2003.

[6] D. R. Cox. Regression models and life-tables. Journal of the Royal Statistical Society., 34(2):187–220,

1972.

[7] R. Donat, L. Bouillaut, P. Aknin, Ph. Leray and D. Levy, A generic approach to model complex

systems reliability using dynamic graphical models, Mathematical Methods in Reliability, Glasgow,

Ecosse, Juillet 2007.



[8] A. Gelman, J. B. Carlin, H. S. Stern, and D. B. Rubin. Bayesian Data Analysis. Texts in statistical

Science. Chapman & Hall/CRC, second edition, 2003.

[9] C. Huang and A. Darwiche. Inference in belief networks: A procedural guide. International Journal

of Approximate Reasoning, 15(3):225–263, October 1996.

[10]F. V. Jensen. An introduction to Bayesian networks. Press, U. C. L., 1996.

[11] J. D. Kalbfleisch and Prentice R. L. The Statistical Analysis of Failure Time Data. Second Edition.

Wiley Series in Probability and Statistics. Wiley, 2002.

[12]R. Kay. Proportional hazard regression models and the analysis of censored survival data.

Applied Statistics, 26(3):227–237, 1977.

[13]H. Langseth and L. Portinale. Bayesian networks in reliability. Reliability Engineering & System

Safety, In Press, Corrected Proof, 2006.

[14]N. Limnios and G. Oprisan. Semi-Markov Processes and Reliability. Statistics for Industry &

Technology. Springer, 2001.

[15]K. P. Murphy. The bayes net toolbox for matlab, 2001.

[16]K. P. Murphy. Dynamic Bayesian Networks: Representation, Inference and Learning. PhD thesis,

University of California, Berkeley, 2002.

[17]Richard E. Neapolitan. Learning Bayesian Networks. Prentice Hall, April 2003.

[18]L. Podofillini, E. Zio, and J. Vatn. Risk-informed optimisation of railway tracks inspection and

maintenance procedures. Reliability Engineering and System Safety, 2005.

[19]P. Weber and L. Jouffe. Reliability modelling with dynamic bayesian networks. In 5th IFAC

Symposium on fault Detection, Supervision and Safety of Technical Processes, Washington D.C., USA, June

2003.

2.3. ADVANCED MAINTENANCE STRATEGIES (WP2.3 DEVELOPED BY TTK)

The main objective of this work package was to define a list of recommendations on how experiences

from maintenance need to be taken into account when constructing new track sections or when

implementing new systems.

2.3.1. Introduction

The introduction of essential maintenance aspects in the design/construction phase is quite new for

European tramway networks today. In the past years, few were the number of call for tenders for the

tram infrastructure construction that included a thorough chapter of future maintenance of the future

tram infrastructure. More often than not maintenance aspects are neglected during these important

phases of design and construction. This is, however, a necessary step that will need to be applied by



European track networks today in order to avoid unnecessary higher maintenance costs due to

insufficient design or poor construction materials or methods.

This work package searches to study the organisational aspects of track management and particularly the

link between design/construction and operations/maintenance. The final objective of this deliverable is

to present a list of recommendation and of best practice examples in relationship to the way the

maintenance department within an urban transport operator or separate maintenance company is

handling its resources.

Within this sub-project, the following questions were addressed:

What are the key maintenance questions that need to be addressed before construction?

How can the renewal of different track elements be optimised?

What are the best communication channels between the construction and the maintenance department

that will considerably improve track maintenance?

2.3.2. Methodology

This work package consisted in two main activities:

Research of European and national framework of regulation regarding construction and maintenance of

tramway infrastructure

Interviews with selected European Tramway operators:

Identification of the principal organisational schemes of tram management,

Selection of European Operators for surveying,

Results of the interviews,

Conclusions

Eleven light rail track networks were selected. The sample chosen is constituted of three state-owned

networks (all-in-house activities), four networks where the main activities of design, construction,

operation and maintenance are semi-segregated (i.e. one transport authority and one public transport

company in charge of at least two of the main operations: operation and maintenance, or of all main

operations: construction-operation-maintenance) and three networks characterized by having complete

segregation of main activities (one transport authority, several construction design and construction

consortia, one or several operators and one or several maintenance contractor).



CityTram

network

Begin of

tramwayoperation

Operator/

maintenancecontractor survey

Type of organisational scheme Date

1. DublinLUAS tram

lines

Red line &

green line:2004

Alstom / Veolia

Complete segregation of phases/activities: RPA(RailwayProcurement

Agency) transport authority; various construction and design consortia;Veolia - tram operator; Alstom - vehicle and infrastructure maintenance

contractor

June 28th -29th2007

2. Karlsruhe70 km city

owned

Since 1900(electric

tramway)VBK

All-in-house activities: VBKVerkehrsbetriebe Karlsruhe (100%city

owned) carries out all activitiesAugust 22nd 2007

3. Barcelona T1-T5T3: 2004; T4:

2004; T5: 2005

Two separate tramnetworks: TramBaix

(T1, T2, T3) and TramBesos (T4 and T5)

Complete segregation of phases/activities: Autoritat del TransportMetropolità (ATM): transport authority; various construction and design

consortia (FCC-Vivendi, Comsa y Acciona-Necso), various tramoperators: Soler i Sauret, Sarbus and Connex

Nov 22th 2007

4. Sevilla 1 tram line 2007 Metro Centro

Semi-segregation of phases/activities: Consorcio de transportes del Area

de Sevilla: transport authority; Metrocentro: in charge of operation and

maintenance (partially); CAF - vehicle constructor and maintenancecontractor; Thyssen Group, ASVI, Siemens and Sedra infrastructure

constructor and maintenance contractor

Nov 20th 2007

5. Paris T1, T2, T3, T4T1: 1992;

T2:1997; T3:

2006; T4: 2006

RATPSemi-segregation of phases/activities: STIF (Syndicat des Transportsd'Ile de France): transport authority; various construction and design

consortia; RATP: tram operator and in charge of maintenance

Jan 16th 2008

6. Prague500 kmof

tracks

Since 1891(electric

tramway)

PraguePublic TransitCompany (Dopravni

podnik)

All-in-house activities: Prague Public Transit Co. Inc (100%city owned)

carries out all activitiesApril 28th 2008

7. Bergen (New)

20km of new light

rail between

Bergen's centre and

Bergen's airport

Jan. 07, 2008 -

beginof construction

- inauguration

expected in 2010

Not decided Noavailable information at the moment April 29th 2008

8. LondonLondonTramlink

2000

(Until 2008 operated byTramtrack CroydonLtd

(TCL)) Since then by TfL

London Rail

Complete segregation of phases/activities: TFL (Transport for London)

integrated bodyresponsible for London's transport system; various

construction and design consortia; TCL as the owner of TRamlink has a99 year concession. First Group - tram operator; TCL- infrastructure

maintenance and Bombardier Transportation - vehicle maintenance

Feb. 12th, 2009

9. Strasbourg 4 tram lines

A: 1994; B:2000; C:2000;D: 1994; E:

2007

CTS

Semi-segregation of phases/activities: CUS(Communauté Urbaine de

Strasbourg): transport authority; CTS(Compagnie des TransportsStrasbourgeois): in charge of operation and maintenance (concession

contract: 1990-2020)

Mai 12th 2009

10. FlemishRegion

Tram (128,3km)

Since 1894

(electrictramway)

DeLijn All-in-house activities: run by the Flemish government in Belgium June 23rd, 2009

11. Lyon TCLT1: 2001; T2:

2001Keolis

Semi-segregation of phases/activities: SYTRAL (Syndicat mixte desTransports pour le Rhône et l'Agglomération Lyonnaise): transport

authority; various construction and design consortia; Keolis: tram operatorand in charge of maintenance

July, 2009

Interviewsexecution:

duringthefirst yearof research

duringthesecondyearof research

duringthethirdyearof research

All-in-houseactivities

semi-segregationof activities

Completesegregationof activities

Typeof orgnisational scheme:

Tab. 2.3.1: Selected networks surveyed



2.3.3. Conclusions

After carrying out eleven interviews with different European tram operators, all with very different

organisational schemes of transport management, we can present the following conclusions:

Importance of a tool of internal maintenance knowledge: the real knowledge of the tracks’ conditions is

being held by a reduced number of personnel (tracks’ conditions and development).

Keeping good channels of communication between the maintenance and the construction department:

The closer the relationship between the maintenance and the construction department the better it is for

implementing accurate maintenance plans and for producing more efficient track design.

Different organisational schemes produce different overall public costs (construction + operation +

maintenance): The way of conceiving public transport services VARIES CONSIDERABLY according to

the organisational scheme chosen. For each scheme different human, technical and financial resources are

required. Each scheme has its advantages and disadvantages regarding overall costs, level of

transparency and level of implication and responsibility of the contracting authority.

General tendencies regarding track management

The tendency of externalising all responsibilities regarding tram operations and track management is

reversing in some European countries. Old questions seem to arise once again regarding the advantages

and disadvantages of state-owned companies and private companies of urban transport services and

regarding the exact role of transport authorities in assuring public transport services.

In general two major tendencies regarding coordination and direction of main transport activities are

identified in the discussions with the operators:

The operators, within in-the-house operations organizations and usually being 100% public owned,

assure directly the major tracks of overall control and coordination. The transport authorities have in

charge of all main activities of design/construction, operation and maintenance, they decide which

activities to externalise but they keep control of these activities at all times (examples of such schemes:

Karlsruhe, Prague and De Lijn).

The transport authorities coordinate themselves all the different contracts with the respective companies

in charge of construction, operations and maintenance or deals directly with one consortium in charge of

all main activities. (BOT – Build, Operate and Transfer – schemes; examples of such schemes: Dublin,

London – before 2008 and Barcelona).

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