Evaluation of safety and operational impacts of bicycle bypass lanes at modern roundabouts

Abstract

Modern roundabouts have been found to improve safety and reduce overall delay, but they may have negative impacts on the safety of cyclists as other vehicles may cut-off cyclist paths while entering or exiting the roundabout. Sev- eral before–after studies have found an increase in traffic collisions involving cyclists at roundabouts after being converted from conventional signalized intersections. Another concern associated with roundabouts is the safety of pedestrians, espe- cially pedestrians with severe vision impairment who may find difficulty in negotiating roundabouts. This paper evaluates safety and operational impacts of using bicycle bypass lanes at roundabouts as a means of increasing the safety of cyclists. The paper also recommends the full utilization of pedestrian traffic signals, proposed by other studies, by incorporating them with the proposed bicycle bypass lanes. An evaluation scheme involving the safety benefits and the costs of the pro- posed bypass lanes is provided to help practitioners decide when they are warranted. The evaluation scheme is illustrated using an application example.