The Adelaide O-Bahn Busway is a guided busway located in Adelaide, South Australia. The O-Bahn – from the Latin omnibus ("for all people") and the German bahn (railway, as in S-Bahn and U-Bahn) – was conceived by Daimler-Benz to enable buses to avoid traffic congestion by sharing tram tunnels in the German city of Essen. The route was introduced in 1986 to service Adelaide's rapidly expanding northeastern suburbs, replacing an earlier plan for a tramway extension. The Adelaide O-bahn was the first bus rapid transit system in Australia and among the first to operate in the world.
The O-bahn design is unique among public transport systems; busways typically use dedicated bus lanes or separate carriageways, but the O-Bahn runs on specially built track, combining elements of both bus and rail systems. Adelaide's track is 12 kilometres (7.5 mi) long and includes one station and two interchanges: Klemzig Station in Klemzig, Paradise Interchange in Campbelltown and Tea Tree Plaza Interchange in Tea Tree Gully. Interchanges allow buses to enter and exit the busway and to continue on suburban routes, avoiding the need for passengers to change. Buses travel at a maximum speed of 100 km/h (62 mph), and the busway is capable of carrying 18,000 passengers an hour, from the Central Business District to Tea Tree Plaza in 15 minutes. Services are operated under contract from Adelaide Metro, an agency of the South Australian Department for Transport, Energy and Infrastructure.
It was planned that bus routes serving the O-Bahn would be enhanced from Hackney Road along Grenfell and Currie streets and extended to West Terrace on the far side of the CBD along dedicated bus lanes. However, the Federal Government announced in January 2011, as part of its response to the 2010–2011 Queensland floods, that the extension would be cancelled "as a result of a significant scope reduction of the original project, resulting in only limited transport benefits".