Discussion Document No 011
This document is published to stimulate discussion and does not necessarily represent the views of the LRTA
December 2003
| | Light Rail Transit Association - UK Development Group Discussion Document No 011 This document is published to stimulate discussion and does not necessarily represent the views of the LRTA |
December 2003 |
INTRODUCTION
For well over 100 years the world has seen some completely different methods for supplying power to LRV's and trams. Some of the early experiments, in Lincoln for example, used studs between the rails and controlled them by a mechanism that only energised a stud when a tram was directly above it. Unfortunately many a horse suffered a nasty electric shock when the safety aspect of the mechanism failed. The unreliability of this method soon caused it to be replaced with the more conventional overhead conductor wire.
For many years a large part of Central London used another method, the underground conduit system, which powered the tram without any overhead wires. In the outer suburbs a more conventional overhead wire was used but unfortunately the change-over pits tended to be labour intensive and needed an operator at every pit. This method continued until the end of the system in 1952.
The world-wide revival of the tramway concept in urban locations has renewed the environmental objections to overhead wires, especially in some historic town centres. Bordeaux in France is one such case and much time and money has already been spent in developing an efficient fail-safe ground level power supply for its future tram system.
A FIRST - BORDEAUX's MODERN GROUND LEVEL SYSTEM
This French seaport had originally planned to build an automated VAL light metro system but, not unlike Strasbourg, was mainly controlled by officials with diverging political and transport views. The city eventually settled for some form of light rail. A consortium led by Alstom was eventually selected to build the first phase of a 3-line light rail system with the Turnkey contract method and targeted for a 2003 opening. Alstom will supply the air conditioned CITADIS low-floor trams made up of 32 at 40 metres (300 passengers) and 6 at 30 metres (200 passengers). Another option included in this contract was a total maintenance arrangement covering the first 10-years of operation. This could be helpful in Bordeaux as the consortium suggested the ground-level system through the historic part of the city (1).
A TECHNICAL AND AESTHETICAL SHOWCASE
It is hoped that a combination of track paving and grass will blend in with the light rail system and help to generally revitalise this historic city. The new INNORAIL ground level power supply system will cover about 10.5-km of street running in the city centre. Only the section directly beneath the tram will become energised and activated from an antenna around the pick-up shoes. The live sections are 8-metres long and separated by 3-metre long neutral sections fitted with plastic contact strips to provide a continuous running surface for the pick-up shoes. The actual change-over from one system to the other will for simplicity be done by the driver at station stops. INNORAIL though is so designed that it can operate at up to 70-km/h with a mode change being possible whilst on the move. Should INNORAIL fail, each vehicle has batteries on the roof to permit about 1-km of operation at low speed. The minimum curve radius in the city centre is 18-metres and flange greasers will be used to keep noise levels to a minimum. The maximum specified noise level is 74-dB which compares with the French "norm" of 78-dB (2).
SOME OPERATIONAL DETAILS
The system will be operated by CONNEX and the hope is that 25% of car users in Bordeaux will be attracted to it. During peaks periods the vehicle frequency will be every 4-minutes and every 8-minutes off-peak. Services will operate from 0500 until 0100 leaving just 4-hours for routine maintenance.
A MAJOR ENVIRONMENTAL BREAKTHROUGH
The environment has gained much from Bordeaux's experiments because any new tram system up to the present time not permitted to use overhead wires would have been limited to cable or diesel power. Fortunately this has now changed the situation and an electrification upgrade to satisfy increased passenger demands is unlikely to create new environmental concerns. Also, a partial use of INNORAIL could overcome environmental concerns in some of our historic towns and cities such as Bath, Chester, Lincoln and York.
ENERGY STORAGE FOR TRAMS
As this Discussion Document was being prepared, a roof mounted storage system was reported (3) as being developed by Bombardier Transportation. This new storage facility, called MITRAC ENERGY SAVER, stores the energy recaptured during the braking mode (up to 30%) for re-use. Two energy saving units linked together could be sufficient to propel a tram for 1000-metres with its pantograph lowered. It may also be useful in an environmentally sensitive location.
CONCLUSION
All transit operators throughout the world will be following closely the success or otherwise of Bordeaux's innovative tramway system. Preliminary indications point to resounding success and places with laws forbidding overhead pick-up wires (Washington for instance) should now be able to deal with their almost grid-lock traffic conditions.
REFERENCES
The December 2003 issue of TRAMWAYS & URBAN TRANSIT - page 460 has just revealed that public service should start on 20th December 2003.
Prepared by F A Andrews for the LRTA Development Group December 2003
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