Turbo roundabouts are multi lane roundabouts with physical separators on the approach and through the circulating carriageway. The design requires turning drivers and motorcyclists to position themselves in the appropriate lane on the approach to the roundabout.
Turbo roundabouts reduce vehicle speed through the roundabout (can’t take a straight line through) and reduce lane change crashes due to the channelisation. They can reduce crashes by up to 76% (Fortuijn 2009).
Some key design considerations that differ from a conventional roundabout; drainage, large vehicle swept paths, advanced directional signage, lighting and delineating the raised separators.

Images credits: adapted from FHWA, DHV & Brian Moore