Nancy & Caen

Northbound TVR tram leaving Résistance station in Caen. Photo by Duncan Allen.

Two French cities were the first to operate the Bombardier TVR (Transport sur Voie Réservée) technology, also known by the English acronym GLT (Guided Light Transit). TVR is the first 'tram sur pneus' or rubber-tired tramway technology to see revenue service¹.

The first TVR system in service (December 2000) was in Nancy, the capital of the département of Lorraine. The local transit operator, STAN (Société de Transports de l'Agglomération Nancienne), was experienced with trolleybus operation, but wanted higher speed and capacity, and (apparently) to have something they could call a 'tramway' after Strasbourg (the capital of next-door Alsace) began tram service in 1995. There was considerable debate about conventional trams versus TVR; STAN seems to have selected TVR for low first cost (initially indicated as 35-40% less than LRT), minimum horizontal curving ability (39 feet), and gradeability (13%).

Over about 40% of the city's single tramway route, the Nancy trams operate in a free-wheeling ('routier') mode, without the central guiderail Transition from guided to 'routier' mode occurs in motion, with a noticeable (but not objectionable) bit of bumping and noise. Transition from free-wheeling to guided mode requires a full stop before a special set of street-mounted hardware, then operating the vehicle over it slowly for its entire length² until all the guidewheels are successfully engaged. Some minor noises occur during this process. In 'routier' mode, the driver steers the vehicle, and the general ride quality and noise level are indistinguishable from a conventional articulated trolleybus. Both the Caen and Nancy vehicles are equipped with steering wheels (which move on their own 'hands free' during guided operation), and can use an auxiliary diesel motor for movements off the overhead contact system (OCS).

The system in Caen began operation in November 2002. The alignment in Caen also has steep grades and tight curves³. The steepest grade apparent on the Caen alignment is shared by both CNG and diesel buses. Caen's public transportation authority (syndicat mixte des transports en commun de l'agglomération caennaise, VIACITES) has contracted for urban system operation (including buses) with Compagnie des Transports de l'Agglomération Caennaise (dubbed 'Twisto'⁴), whose logo is on the vehicles.

The four-axle double-articulated TVR vehicles for Nancy and Caen are nearly identical, with characteristics as shown in Table 1. Braking and propulsion are controlled by the operator with pedals, similar to a bus or modern LRV. In their prevailing mode of operation, horizontal guidance is provided by a single central rail. Ahead of or behind each axle, a pair of double-flanged wheels rides on the central rail, held in place by hydraulics applying about 70 kN of force. A steering framework links the forward-placed guide wheels to the trailing axles. The guide wheels appear to run through special work on their flanges. Switches and other special work resemble single-rail versions of conventional duorail systems. The flangeways on either side of the guidance rail are narrow enough to preclude bicycle tires being trapped.

The Nancy vehicles collect power from a pair of overhead trolley wires, using trolley poles and shoes - indistinguishable from a conventional trolleybus. Caen uses a single overhead contact wire, usually in a single-messenger catenary configuration; power return is via the guidance rail.

On 'guided' portions of the route, the wheel paths are often given a visually and texturally distinctive pavement treatment, and are reinforced by an underlying metallic grid ('nid d'abeille') to prevent 'ruttting' of the roadway surface. The distinct appearance may also improve safety in environments accessible to pedestrians.

Ride quality in guided mode seems marginally lower and interior noise marginally higher than modern LRT, but there is no rail squeal on curves. It is generally comparable to VAL or the rubber-tired metro lines in Paris and Montreal.

Although TVR can be regarded as a 'proven' mode at this point, both Nancy and Caen have had their share of 'teething problems', and it would not be appropriate (as of the summer of 2004) to apply the label 'mature'. Nancy took their system out of service for a full year (March 2001- March 2002) after two incidents involving the rear section of the vehicle sideswiping OCS poles upon the transition from guided to free-wheeling mode. Bombardier made some retrofits, and incorporated them in the Caen vehicles. The French national transportation authorities were prompted by seven⁵ less significant 'losses of guidance' (six in Nancy and one in Caen) and one tire explosion (in Caen) during 2002 to conduct a study of TVR guidance system safety. The report⁶ recommended more frequent inspections of many system elements and strict adherence to maximum authorized speeds in curves, and suggested that the steel guidewheels may be too hard relative to the guiderail surface. Research to develop means to better manage tire and guiderail wear was also suggested.

Local news items suggest that vehicle availability has also been an issue (14-16 available out of 24 in Caen at one point in 2003). Caen's system has decals on the trams explaining to passengers how to get to replacement or supplementary buses ('bus de renfort') when (unspecified) things go wrong with the tramway. Supplemental service has also been required in Nancy when insufficient vehicles are available. The general attitude of the riding public might be summed up as: "When it's running, and if there are enough vehicles, it's pretty cool".