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Arubber-tyred tram (also known astramway on tyres,French:tramway sur pneumatiques) is a development of theguided bus in which a vehicle is guided by afixed rail in theroad surface and draws current from overhead electric wires (either viapantograph ortrolley poles).
Two incompatible systems using physicalguide rails exist: theguided light transit (GLT) designed byBombardier Transportation, and thetranslohr fromLohr Industrie (currently made byAlstom and FSI). There are noguide bars at the sides but there is a centralguidance rail that differs in design between the systems. In the case of Translohr, this rail is grasped by a pair of metal guide wheels set at 45° to the road and at 90° to each other. In the GLT system, a single double-flanged wheel between the rubber tyres follows theguidancerail. In both cases, the weight of the vehicle is borne by rubber tyres to which the guide wheels are attached, which make contact with the road on concreteroll ways designed to minimise impact on the ground. Power is usually supplied byoverhead lines, rechargeablebatteries, orinternal combustion engines where there are no overhead wires.
The Translohr system operates as a guided vehicle at all times, while with the Bombardier system the vehicles could be driven independently as requirements dictated, such as journeys to the depot. Consequently, the Bombardier vehicles were legally considered buses, had to be fitted withrear-view mirrors,lights andnumber plates, and were controlled withsteering wheels andpedals like ordinary buses, though the steering wheel was not used when following the guidance rail. On the other hand, Translohr vehicles operate like standardtrams and cannot move without guidance, so they are not classified as buses and are not equipped with number plates.
These systems have been likened to the tram equivalent ofrubber-tyred metros, and they are also less efficient than steel-wheeled light rail vehicles. There is no evidence to prove the superiority of either guidance system. Both Bombardier and Translohr have hadderailments during operation.[1][2]
| Feature | TVR in Nancy | TVR in Caen | Translohr |
|---|---|---|---|
| Principle |  Diagram of theguide rail and guide wheel of the Bombardier's GLT | Diagram of theguide rail and guide wheel of the Bombardier's GLT |  Diagram of the Translohrguide rail (green) and the tram's guide wheels (red) |
| Lane guidance | Partially | Continuous, except access to the depot | Continuous |
| Overhead line | Two-pole | Single-pole | Single-pole |
| Return current via guide rail | No | Yes | Yes |
| Pantograph | Two poles | Single beam | Single beam |
| Operating mode | Interior trolley | Interior trolley | Bidirectional cars |
| Outline | Three-part | Three-part | Three-, four-, five- or six-part |
| Articulated portal | No | No | Yes |
| Multiple traction possible | No | No | Yes, double traction |
| Vehicle registration number | Yes | Yes | No, except in Shanghai |
| Auxiliary drive | Diesel | Diesel | Battery |
| Use without guide rail | Yes, freely steerable (with overhead line or auxiliary drive) | Yes, freely steerable (only with auxiliary drive) | No, not freely steerable |
