What's my line? Am I a bus or a trainl
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Mercedes O-Bahn buses use permaneni way or public roads. Will we ever see them in operation? Noel Millier investigates
IS IT A BUS or is it a train? It is both! It's a vehicle on the West German O-Bahn system being developed by Daimler-Benz as a more economical solution for public transport than expensive rail-based mass transit systems.
This system combines the inherent economy of the conventional bus with the speed and efficiency of reserved track and automated rail operation. However, when I first heard of 0Bahn I thought it illogical to introduce new elements such as tracks and guideways to bus operation. Simplicity to an extent breeds reliability and a conventional bus system coupled with good roads and traffic management must be favourite in terms of a cheap and reliable public transport system.
As an alternative to the conventional bus, O-Bahn offers little, but as an alternative to the tram or train and integrated with conventional bus services the system could prove both attractive and reliable. Daimler-Benz started the research project in 1977 and the concept is now in use in Essen in West Germany and is to be adopted in Adelaide in South Australia.
Daimler-Benz claims that with O-Bahn it could be possible to introduce a public transport system that requires little subsidy.
Essentially, O-Bahn is a rail system where passenger trains and their rails are replaced with bus-derived vehicles on concrete guideways.
At Rastatt the test facility allows the use of either electronic or mechanically guided buses to operate totally automatically over the sections of guideway while still retaining the flexibility of normal operation on public roads.
The facility includes a section of guideways in tunnels and on elevated tracks; three types of switches for mechanicall switching the direction of bus( and two electronic ones; a (I vice to absorb exhaust gase and an overhead line for electi cally powered buses as well E an operational control centre.
With the electronicall controlled guidance systei buses are controlled by a cab fitted into the track. A sens( mounted on the front of the measures the signal from if cable which is fed into the bt hydraulic system. In this way if position of the vehicle's froi wheels is adjusted so that it ft lows its desired course. Th vehicle is fitted with a number ( safeguards to overcome the po: sibility of system failure comprc mising safety.
With the mechanicall controlled systems, buses ar controlled by either lateral guid rails, or horizontal guide roller on supporting wheels. Th system using guide rails hE been developed to series or( duction stage and is in use in th City of Essen.
A forced guidance system fc
buses only available for use on the guideway has been developed. With this system all wheels are guided by horizontal guide rails and the vehicle can be operated without a driver or even a steering wheel.
Daimler-Benz has developed a high-capacity double articulated bus for use on the guideways only and this can be coupled to other vehicles to form trains. Although built by using modules from standard bus designs, the high-capacity vehicle has more in common with rail-bound vehicles than standard dieselpowered buses. It is two directional and has a driving compartment at each end. It is powered by electricity supplied to AEG-Telefunken equipment by means of an overhead line and a pantograph.
This big artic bus has four axles and is powered by two 250kW electric motors. Return current is collected by brushes and live lateral rails integrated into the guide rails. The total vehicle is considerable lighter and therefore more energy efficient than the equivalent rail vehicle and is capable of stable operation up to 1 0 Okm/h (64mph).
For conventional two-axle or three-axle articulated buses, vir
tually any type of drive system can be used.
For underground operation of diesel-powered buses where tunnel ventilation is not installed, a special "suck-off system" has been developed to allow engine exhaust gases and cooling air to be guided upwards and carried off in a longitudinal channel before being mixed with other air in the tunnel.
The O-Bahn concept allows for almost any degree of centralised vehicle control — from simple two-way radio to completely centralised vehicle control — which can control vehicle speeds and ensure that they maintain a safe distance from each other.
Driverless operation is possible using the control system being developed and tested at Rastatt.
Track elements at the test track show that the system can work with a number of types of surface including prefabricated concrete sections developed by German civil engineering group Zublin AG.
Ground-level construction costs for the O-Bahn track are more expensive than for roads and about the same as for railways, although underground tunnels can be half the cost of road tunnels and 25 per cent cheaper than railway tunnels.
Elevated tracks are 40 per cent cheaper than rail tracks using the same prefab concrete elements.
Biggest savings result from the fact that 0-Bahn needs less track maintenance and less guidance systems than conventional railway systems.
Three kinds of systems to switch buses from track to track are being tested at Rastatt des pite the fact that the concept allows buses to switch from automatic guidance to manual steering with ease. The three types of switches are: A lifting guide rail switch operated by the lowering and raising of an electrically operated balance beam, A switch guide rail switch where the guide rails are elastically de formed by hydraulic cylinders fitted to the outside of the guide rails. (This system needs no equipment below the track surface.) Finally, the slot-type switch which is operated with the aid of rollers attached to each steered axle.
0-Bahn is, therefore, being developed as a total transport concept designed to enable a wider market for Mercedes-Benz 0305 city buses to be developed rather than as an evolution of a conventional bus system.
After visiting the Rastatt test track I could think of few immediate applications for such a scheme in Britain although for new and developing cities 0Bahn could go some way towards defeating the problems of capacity created by limited peakhour needs. For example, an 0Bahn system could be introduced with a limited number of double-ended high-capacity electric powered buses to meet the off-peak service requirement which could be supplemented by more conventional rigid or articulated buses during the peaks.
These buses, which could be either diesel or hybrid type vehicles, could then be used for conventional on-road duties during the off-peaks.
The concept allows for as much sophistication as each individual application merits.
I am sure that there are a few problems to be overcome before 0-13ahn becomes readily acceptable, but the concept, with its use of proven bus technology, could lead to light railbased public transport being regarded as an anachronism before the end of this century, and give the world market for buses a long-term boost.