Rubber-tyred tram

Two incompatible systems using physical guide rails exist: the guided light transit (GLT) designed by Bombardier Transportation, and the translohr from Lohr Industrie (currently made by Alstom and FSI). There are no guide bars at the sides but there is a central guidance 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 the guidance rail. 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 concrete roll ways designed to minimise impact on the ground. Power is usually supplied by overhead lines, rechargeable batteries, or internal combustion engines where there are no overhead wires.

Characteristics

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 with rear-view mirrors, lights and number plates, and were controlled with steering wheels and pedals like ordinary buses, though the steering wheel was not used when following the guidance rail. On the other hand, Translohr vehicles operate like standard trams 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 of rubber-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 had derailments during operation.