Guided bus
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Guided buses are buses steered for part or all of their route by external means, usually on a dedicated track. This track, which often parallels existing roads, excludes all other traffic, permitting the maintenance of reliable schedules on heavily used corridors even during rush hours.
Guidance systems can be either physical, such as kerbs, or remote, such as optical or radio guidance.
On kerb-guided buses (often abbreviated to KGB) small guide wheels are attached to the bus, and these engage vertical kerbs on either side of the trackway. The bus is steered in the normal way away from the guideway. The start of the guideway is funnelled from a wide track to the normal width. The trackway allows for high-speed operation on a narrow guideway.
Only a few examples currently exist, but more are proposed in various countries. The longest guided busway in the world is the O-Bahn Busway route in Adelaide, South Australia, which has been operating reasonably successfully since the mid 1980s.
A number of guided busways currently operate in the United Kingdom. They are at:
- Ipswich (Kesgrave) - opened in 1995
- Leeds (Scott Hall Road) - opened in 1995
- Leeds (A64 York Road and A63 Selby Road) - opened in 2001
- Bradford (A641 Manchester Road) - opened in October 2001.
- Crawley (Southgate Avenue) - opened in August 2003.
- Crawley (London Road) - opened in December 2004.
- Edinburgh (Fastlink - Stenhouse to Broomhouse) - opened in December 2004.
In Mannheim, Germany from May 1992 to September 2005 a guided busway shared the tram alignment for a few hundred meters, which allowed buses to avoid a congested stretch of road in a location where there was no space for an extra traffic lane. It was discontinued as the majority of buses fitted with guide wheels were withdrawn for age reasons. There are no plans to convert newer buses.
Rubber-tyred \"trams\"
A further development of the guided bus is the "tramway on tyres", a rubber-tyred vehicle guided by a fixed rail in the ground, which draws current from overhead electric wires like a conventional tram. Two incompatible systems exist, the Guided Light Transit designed by Bombardier Transportation, and the Translohr system. There are no guide bars on the sides but there is a central guidance rail that, in the case of Translohr, is a special rail that is grasped by a pair of metal guide wheels set at 45° to the road and at 90° to each other. In the Bombardier system a single double flanged wheel between the rubber tyres follows the guidance rail. This is why the two systems are not compatible, however the shape of the groove of the double-flanged Bombardier guide wheel could possibly be adapted to the shape of the top of the Translohr guidance rail. In both cases the weight of the vehicle is borne by rubber tyres on bogies to which the guide wheels are attached. Power is supplied by overhead lines, or by rechargable batteries in areas where there are no overhead wires.
The Bombardier system has been adopted in Nancy and Caen, France, while the Translohr system is in use in Clermont-Ferrand, France, and is under construction in Padua, L'Aquila, and the mainland Mestre district of Venice in Italy. The Translohr system is intended for guidance-only operation, while the Bombardier system can be driven as a normal bus as requirements dictate, such as journeys to the depot. The Bombardier vehicles are legally considered buses, and must bear bus-like rear-view mirrors, lights and number plates. Unlike trams, GLT vehicles have a steering wheel, though it is not used when following the guidance rail. Because the Translohr "tram" cannot move without guidance it will probably not be classified as a bus. Hence the Translohr vehicles that on test runs on the Clermont-Ferrand network are not equipped with licence plates.
These systems offer a much more tram-like experience than a regular guided bus, and offer some advantages over trams, such as a potentially smaller turning radius, the ability to climb steeper gradients (up to 13%), and quieter running around corners. The infrastructure installation can be less complicated than the installation of a complete tram line in an existing street. These systems have been likened to the tram equivalent of rubber-tyred metros, and they are also correspondingly less efficient than steel-wheeled light rail vehicles.
Other experimental bus systems have non-physical guidance systems, such as sensors or magnets buried in the roadway.[link]
See also
- Bus rapid transit
- Bombardier Guided Light Transit
- Translohr
- Rubber-tired metro
- Light rail
- Tram
- Dual-mode bus
- VAL
External links
- [Guided bus information and pictures]
- [Adelaide O-Bahn]
- [First Group guided busways]
- [Translohr official site]
- [Guided Light Transit official web site]
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