Guided bus

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O-Bahn Busway in Adelaide
O-Bahn Busway in Adelaide

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 as well as precise positioning at boarding platforms, facilitating access for the elderly and disabled.

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.

The first guided busway in United Kingdom was in Birmingham, branded as Tracline 65 and had a short 600 metre length as an experiment in 1984. It has since been removed. [1]

A number of guided busways currently operate in the United Kingdom. They are at:

Plans for a guided busway in Cambridgeshire met with local opposition, with campaigns such as CAST.IRON advocating the re-opening of the Cambridge to St Ives railway line however in December 2005 the scheme was approved and funding was confirmed late in June 2006 [2]. Construction began in January 2007 and the County Council say that the service "will start to carry passengers in late 2008".

In Mannheim, Germany from May 1992 to September 2005 a guided busway shared the tram alignment for a few hundred metres, 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 It was discontinued as the majority of buses fitted with guide wheels were withdrawn for age reasons.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.

The guide wheel of a guided bus in Mannheim, Germany

A Fastway bus in the guided bus lane on Southgate Avenue, Crawley, UK

Guided buses shared the tram alignment for a short length in Mannheim

Contents

[edit] Rubber-tyred "trams"

Diagram of the Translohr central guide rail (green) and the vehicle's guide wheels (red), which grasp the rail perpendicular to each other, thereby all but eliminating derailments.
Diagram of the Translohr central guide rail (green) and the vehicle's guide wheels (red), which grasp the rail perpendicular to each other, thereby all but eliminating derailments.

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 tires 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 rechargeable 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 Tianjin, China, 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.

A Translohr rubber-tyred "tram" for the future system in Padua, Italy
A Translohr rubber-tyred "tram" for the future system in Padua, Italy

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-tired metros, and they are also correspondingly less efficient than steel-wheeled light rail vehicles. On the negative side, there have been significant technical difficulties in Nancy since the system opened with "derailments", where the guidance system becomes detached from the central guide rail.[1]

Some commentators believe that rubber-tyred "trams" share the same problems of negative perception as other bus rapid transit systems.

Other experimental bus systems have non-physical guidance systems, such as sensors or magnets buried in the roadway.[3] In 2004, Stagecoach Group signed a deal with Siemens AG to develop an optical guidance system for use in the UK.[2]

[edit] References

  1. ^ "Further problems in Nancy", LRTA, November 20, 2002.
  2. ^ "Stagecoach signs deal with Siemens to develop new bus optical guidance system", Stagecoach Group, December 8, 2004.

[edit] See also

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[edit] External links

Buses
Articulated bus – Double-decker bus – Guided bus – Gyrobus – Low-floor bus – Midibus – Minibus
Motorcoach – Party bus – School bus - Transit bus – Trolleybus
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