Simulation Study of Access Management at Modern Roundabouts: Treatments of Pedestrian Crosswalks

The widespread emergence of modern roundabouts in North America has kindled a controversy about pedestrian access. Almost uninterrupted traffic streams, ambient noises, and urban settings make it difficult for the visually impaired to perceive safe crossing gaps when only auditory cues are used. In 2005, the U.S. Access Board released a revised draft guideline calling for the provision of a “pedestrian-activated traffic signal … for each segment of the crosswalk” to ensure access for vision-impaired pedestrians. The Access Management Manual prescribes major transportation actions encompassing multimodal streets with sidewalks and adequate pedestrian refuges, but the manual does not address the issue of pedestrian access at roundabouts. In North America few roundabouts have been outfitted with pedestrian signals. Little research has explored signalizing roundabouts for pedestrian access improvements. This simulation study quantitatively assessed the performance of four pedestrian signals placed at roundabouts with a wide spectrum of test scenarios resulting from varied crosswalk layouts, installation schemes, and operational conditions. A two-stage installation scheme was found more operationally efficient than a one-stage scheme; with the two-stage scheme, no significant differences existed between three layouts. When a one-stage scheme operated, a distant layout reduced vehicle delay and queue length because of enlarged storage space. High-intensity activated crosswalk signals induced minimum vehicle delay, and pedestrian user-friendly interface signals minimized pedestrian delay while fully protecting pedestrians. The findings provide an objective basis for identifying crosswalk treatments to improve roundabout accessibility and are informative for transportation policy makers, planners, and practitioners in the access management community who work at enhancing roundabout accessibility for pedestrians.