Roundabout geometric design guidance.

This report examines geometric standards, guidelines, and practices, both on a state level and a national level), for developing recommendations on roundabout design guidance for California. The research involved assessing the operational performance of various California roundabouts and developing calibrated capacity models that are consistent with recent national research. A calibrated intersection sight distance model was also developed. Pedestrian and bicycle behavior at existing California roundabouts was examined, and their performance was compared to national observation. Finally, a range of recommendations on geometric design parameters were developed, including vehicle speeds, design vehicle, inscribed circle diameter, and issues related to roundabouts with more than four legs, roundabouts at freeway interchange terminals, and roundabouts in high-speed environments.