Cyclists in roundabouts--different design solutions.

Whether the safest roundabout design for cyclists is to separate cycle crossings or integrate cyclists with motorists is an extensively discussed issue. Studies using accident statistics indicate that a separated cycle crossing is the safest for high motor vehicle volumes. However, the results have not been satisfyingly explained. This article combines quantitative and qualitative methods in traffic conflict, interaction and behavioural studies to find out how interactions and conflicts differ between the two roundabout designs. Automated video detection is used as one of the methods and its performance is evaluated. The integrated roundabout turns out to be more complex with a higher number of serious conflicts and interaction types. The most dangerous situations in the integrated roundabout seem to come about when a motorist enters the roundabout while a cyclist is circulating and when they are both circulating in parallel and the motorist exits. The yielding rules are more ambiguous in the separated roundabout, contributing to a lower yielding rate to cyclists and a lower trust in the other road user's willingness to yield. Situations in the separated roundabout with the lowest yielding rate to cyclists occur when the motorist exits the roundabout at the same time as cyclists are riding in the circulating direction and hence coming from the right. However, most of the accidents in separated roundabouts occur while cyclists are riding against the circulating direction, both when motorists enter and exit the roundabouts.