Evaluation of Pedestrian Crosswalk Spacing at Roundabouts based on Shockwave Theory

One important aspect of roundabout design is the interaction between vehicles exiting the roundabout and pedestrians crossing the exit roundabout leg, as this can result in queuing of vehicle in the circle, as well as have safety implications for pedestrians. This research analyzes roundabout crosswalk spacing as a function of traffic flowrate exiting the roundabout. The shockwave theory is used for developing an analytical procedure for calculating the crosswalk offset from the roundabout circle. A comprehensive microsimulation model encompassing 147 unique intersection condition combinations was run, comparing the standard roundabout design to the proposed crosswalk spacing. The evaluation was performed based on average vehicle delay, average vehicle stops, average vehicle speeds, and average vehicle stop delay. The conditions presented looks at a single-lane roundabout with posted speed limit of 35 mph and circulation speed of 25 mph. The results demonstrated significant benefits from the proposed design, yielding a reduction in average vehicle delay up to 66.2 sec/veh, reduction in average vehicle stops up to 3.1 stops/veh, reduction in average vehicle stop delay up to 21.1 sec/veh, and an increase in average vehicle speed of 1.3 mph. In addition, the proposed increase in crosswalk spacing does result in the increase of the pedestrian walking time, but these increases are acceptable up to 78 ft offset. Findings discussed in this paper supports roundabout crosswalk design should be spaced further than the standard recommended minimum (20 feet), particularly in the case when the exit flowrate is greater than 600 veh/h/lane.