Here in Adelaide we have the o-bahn guided busway (picture related). Buses drive onto the tracks and have guide wheels on either side which automatically steer the bus.

It works well as a way to get buses out to the suburbs quickly but the traffic along the corridor would probably be better served by a tram system.

I was wondering if a combined system would be possible: a guided busway that uses the tram tracks as the guideway. Has anything similar been developed?