An unusual transit system in Australia combines the flexibility of buses with the speed and smoothness of rail. In Adelaide, South Australia, the O-Bahn, a hybrid of a bus and rail system, connects downtown to the northeastern suburbs.

 

O-Bahn buses drive on fixed guideway bus lanes that steer the buses for the drivers.  Once the buses reach the suburbs, they fan out onto conventional streets, eliminating the need for passengers to transfer to other buses.  This is the O-Bahn’s primary advantage over streetcars and other rail transit.

As these express buses leave central Adelaide on conventional city streets, they cross the city’s historic ring park and travel a mile with general traffic until they enter the bus-only O-Bahn.  The O-Bahn is a set of concrete running pads set far enough apart to carry the buses’ rubber tires. The outward-facing wheels run along the guideway’s curbs and steer the bus for the bus driver.

O-Bahn bus with exterior guide wheel. Photo by the author.

O-Bahn curving through suburban Adelaide. Photo by the author.

Why not build a normal bus-only road?

The O-Bahn provides a few advantages over a conventional bus lane.  The automatic steering means the bus pavement can be narrower, since there’s no need to account for driver error. This is important as the buses can reach speeds of 60 mph.  The O-Bahn runs through a linear park along the River Torrens and minimizing the environmental impact was a significant consideration when the state government selected the mode in the 1970s.

This slightly narrower guideway will come in handy as the state government extends the O-Bahn through a proposed tunnel under the historic ring park that encircles the central city.  A narrower tunnel requires less disruption to the parkland above.

Much like rail, the fixed guideway’s construction provides for a smoother ride, but this is only a marginal advantage over an ordinary concrete road.

For more on transit developments in other cities and around the world, check out Greater Greater Washington’s articles about Cape Town, Dallas, Hartford, Johannesburg, Oakland airport, San Diego, and San Juan.