The 12.6 km Adelaide O-Bahn that was completed in 1989 was the first full-scale application of guided busway technology in the world. The facility serves the northeastern suburbs of Adelaide and was built instead of a previously planned light rail transit (LRT) line. Around 120 million bus km of revenue service has been operated on the busway, with relatively few incidents. The Adelaide O-Bahn has proved to be a more effective and efficient solution than the previously planned LRT – and also more efficient than the lightly used and costly railway network that serves the other major corridors of the metropolitan area of Adelaide. Despite these advantages, the entrenched position of the railways has prevented the wider use of busway as an alternative to the rail lines as major investment in the latter became due. However, the current 3 km extension of the O-Bahn into the city core will complete a missing link. Two valuable features of the O-Bahn are the ability of buses to serve suburban areas and then travel directly onto the guided track and the higher-frequency service compared with the use of larger LRT vehicles. These attributes provide users with a particularly attractive service. In addition, the location of the O-Bahn and the services that use it match the structure of urban development in the region it serves. The integration of the O-Bahn and land use is reinforced by the location of the outer terminus of the busway at a major regional shopping centre and the development of park and ride stations at intermediate interchanges. This chapter describes the history of decision making that resulted in the O-Bahn; its features; its patronage, operational and financial performance; and the land-use context that has underpinned its success.