Adelaide O-Bahn

The O-Bahn Busway is a guided busway that is part of the bus rapid transit system servicing the northeastern suburbs of Adelaide, South Australia. The O-Bahn system was conceived by Daimler-Benz to enable buses to avoid traffic congestion by sharing tram tunnels in the German city of Essen.

Adelaide's O-Bahn was introduced in 1986 to service the city's rapidly expanding north-eastern suburbs, replacing an earlier plan for a tramway extension. The O-Bahn provides specially built track, combining elements of both bus and rail systems. Adelaide's track is long and includes three interchanges at Klemzig, Paradise and Tea Tree Plaza. Interchanges allow buses to enter and exit the busway and to continue on suburban routes, avoiding the need for passengers to transfer to another bus to continue their journey. Buses can travel at a maximum speed of , but are now restricted to 85 km/h (53 mph). , the busway carried approximately 31,000 people per weekday. An additional section including a tunnel opened in 2017 at the city end to reduce the number of congested intersections buses must traverse to enter the Adelaide city centre.

The development of the O-Bahn busway led to the development of the Torrens Linear Park from a run-down urban drain into an attractive public open space. It has also triggered urban development around the north-eastern terminus at Modbury.

Track

The O-Bahn track is made of concrete; it is elevated from the ground because of the poor quality of alluvial soils along the River Torrens, which frequently move due to their high level of plasticity. On top of the pylons are concrete sleepers on which the track rests. 5,600 pylons were drilled in place to support 5,600 sleepers and 4,200 prefabricated L-shaped track pieces, sited at intervals. Concrete pylons were cast into the ground to ensure stability, to a depth of up to . The width of both tracks, sitting on the sleepers, is .Northeast Busway Project (Brochure). South Australian Department of Transport (1983).Busway Information, Paper Two: O-Bahn Guided Bus Concept. South Australian Department of Transport (1983). The O-Bahn's concrete tracks were narrower and lighter than those of the initially proposed light rail development, and put less stress on the land. The concrete components were precast and then laid onto piers.

At the city end, the O-Bahn begins at East Terrace, as an extension eastwards from Grenfell Street into the parklands. The O-Bahn enters an tunnel, completed in December 2017, which curves from east to north, emerging onto bus lanes in the middle of Hackney Road just north of the intersection with Botanic Road and North Terrace. The bus lane continues north to the Torrens River and into the original entrance of the O-Bahn on Hackney Road, opposite the East Parklands, where it enters a tunnel at a speed limited to , due to the tight initial corner, ensuring that the rear tyres (especially trailer tyres of articulated buses) do not 'scrub' against the track. Speed is gradually increased to for most of the trip to Klemzig Interchange. Once en route to Paradise Interchange, the speed limit was up to , but has been limited to since late 2012. On some sections was achieved in tests. The average service speed including stops is about . On entering interchanges the O-Bahn ends and the speed limit is . In the interchange area, the speed limit is . The O-Bahn is officially considered a road, due to a court ruling in the early years of the system's operation. This ruling permits the South Australia Police to install speed cameras and fine speeding drivers.

Cars entering the O-Bahn are deterred by a large number of signs at entrance points and a sump buster device that rips out a car's sump (oil pan) if it gets onto the track. An average of four cars per year enter the O-Bahn and must be removed by crane.

Buses

The first buses to enter service on the O-Bahn were 41 rigid and 51 articulated Mercedes-Benz O305s. These were modified for O-Bahn use by Mitsubishi Motors plant before being bodied by Pressed Metal Corporation South Australia. The cost was included in the original $98 million budget. Modified MAN SG280s and SL202s were later purchased.

With the Mercedes-Benz O305s approaching their 25-year age limit, tenders were called in 2007 for replacements. The new buses were Scania K230UB rigid and Scania K320UA articulated buses bodied by Custom Coaches. , these, along with rigid Scania K280UB/K320UB buses, articulated Scania K360UA buses, one diesel/electric hybrid Scania K320UB, and one Mercedes-Benz O405NH make up the fleet.

In the case of breakdowns, a specially designed vehicle nicknamed 'Dumbo' is used to tow buses from the O-Bahn. In the early stages of design it was intended that all buses would have towing ability; however, this was soundly rejected by the drivers' union and 'Dumbo' was purchased. If a tyre blows during a trip the guide-wheel prevents the bus from erratic movement, and a smaller aluminium inner tyre allows the bus to be driven to the nearest station at .

The guide-wheel, which protrudes just ahead of the front wheels, is the most important part of the bus when travelling on the O-Bahn. It is connected directly to the steering mechanism, and steers the bus by running along the raised edge of the track. While it is not strictly necessary for drivers to hold the steering wheel when travelling on the O-Bahn because of the guide-wheel, safety procedures require the driver to be alert to their circumstances at all times. A rumble strip before stations is a reminder that they need to resume control. The guide-wheel is the most delicate part of the system and is designed to snap off upon sharp impact; before the O-Bahn was in place, a number of buses were fitted with guide-wheels for their ordinary routes to test their durability. Drivers were forced to be more cautious on their normal trips after numerous guide-wheel-to-kerb impacts.

Since June 2018, services are operated by Torrens Transit under contract to Adelaide Metro. , the busway carries approximately 31,000 people per weekday.

Interchanges

Klemzig Interchange is the first station, three kilometres (1.8 mi) from the city centre in the suburb of Klemzig. It was built as a connector to the city loop 'Circle Line' bus service, which followed the Adelaide outer ring route. Many bus services bypass Klemzig and the station has limited capacity. It contains a