Bombardier Guided Light Transit

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GLT vehicles bear a strong resemblance to trams, but are in actual fact buses capable of following a single guidance rail.

Guided Light Transit (also referred to by its French name, Transport sur Voie Réservée or TVR) a public transport system manufactured by Bombardier Transportation and used in the French cities of Nancy and Caen. Though both these cities refer to their networks as ‘tramways on tyres’, the GLT is in fact a model of guided dual-mode bus, capable of both following a central guidance rail and running independently like a conventional bus. GLT is the only model of bus produced by Bombardier’s transport division, which is otherwise focused on rail transport.

1 Characteristics
2 Advantages
3 Disadvantages
4 See also
5 External links

[edit] Characteristics

A central rail embedded in the road guides GLT vehicles while they are in their ‘tram-like’ mode.

transection graph of guide rail and guide wheel

GLT and the similar Translohr are often described as the tram equivalent of rubber-tyred metro technology, but this is not strictly accurate; while the GLT follows a central rail, the rail does not support the vehicle, and the actual wheels which are as independent as those of a regular bus. The wheels of rubber-tyred metros, on the other hand, are bound and guided by their rails in the same way as are steel-wheeled trains.

With two articulation points and a total length of 24.5 metres, GLT vehicles are shorter than most modern trams, but quite long compared to regular buses. They are designed to look much like trams, although they are unidirectional and have bus-like rear-view mirrors. Legally considered buses, they must bear number plates and lights. Unlike trams, GLT vehicles have a steering wheel, though it is not used when following a guidance rail.

They have 100% low floors, seat forty passengers, and have standing room for as many as 105.

Nancy’s fleet use dual trolley poles to collect and return their electric power, in order to allow the use of existing wires constructed for use by trolleybuses. In Caen, where the central guidance rail has been installed on all sections of the passenger-service route, they follow the model used by trams, collecting their power from a single pantograph and returning it through the central guidance rail, and use their diesel motors and steering wheels only while travelling to and from the depot.

The Nancy GLT system is operated by the Société de Transports de l'Agglomération Nancienne, or STAN. The vehicles follow a guidance rail on about 60% of the route. The system entered service in December 2000, but was closed from March 2001 through March 2002 while Bombardier performed upgrades to the vehicles.

In Caen, the GLT fleet began operation in November 2002, incorporating the changes made to Nancy’s vehicles during the upgrade. They are operated by the Compagnie des Transports de l'Agglomération Caennaise under the name Twisto.

[edit] Advantages

Much like trams, GLT vehicles can dock with low station platforms for level boarding.

While the GLT’s central guidance rail is not significantly less expensive than the rails need by regular trams, the overall system can be installed at a lower cost since existing trolleybus wires can be used without the installation of tracks, and not all new sections need have either rails or electric wires installed; even if the entire passenger route is equipped with guidance rails and wires, as in Caen, the depot need not be located immediately by the track, saving planners from having to find space for a new yard in what may be a central and high-valued area of the city.

Another advantage over trams, which was particularly of interest to planners in Nancy, is that rubber tyres give significantly more traction than steel wheels, and so can be used to climb steeper hills, up to a grade or slope of 13%.

Compared to buses, the use of a guidance rail allows GLT vehicles running in parallel lanes to pass closer together than drivers could safely steer. They can also draw up to level, tram-like platforms that allow for easier boarding, and give access to passengers dependent on wheelchairs without requiring the time-consuming deployment of ramps or ‘kneeling’ systems.

[edit] Disadvantages

The GLT systems in place have experienced some mechanical problems which, though they have largely been resolved, have discouraged some other cities from adopting the technology. [1] The vehicles have shown a tendency to move erratically when running free, and do not respond well should the driver mistakenly attempt to steer while following the guidance rail (for example, to avoid a jaywalking pedestrian or an animal running into the street).

Where snowfall is an issue, this system may not be practical.

Critics of the system also point out that unlike a conventional tramway, GLT is a proprietary system, meaning that once having installed it, a city would face difficulties in purchasing vehicles from any manufacturer other than Bombardier. [2] A standard tramway, on the other hand, can easily accommodate vehicles from multiple suppliers; Nancy’s neighbour Strasbourg, for example, recently chose the Citadis tram from Alstom to supplement its existing Bombardier Eurotram fleet.