Exploratory Analysis of Pedestrian Signalization Treatments at One- and Two-Lane Roundabouts Using VISSIM Microsimulation

This paper explores the use of signalized pedestrian crossing treatments at one- and two-lane roundabout facilities. Motivated through increasing debate on the safety of roundabouts for pedestrians, this paper assesses the potential for signalization as a means for regulating the interaction of vehicles and pedestrians at these facilities. The use of pedestrian signals at roundabouts is controversial because of the potential for queue spillback into the circulating lane. This paper aims to quantify the effects of different signalization treatments through microsimulation. The paper uses the microscopic modeling tool VISSIM to estimate impacts on pedestrian and vehicle delay for different crossing geometries and signalization schemes. The range of alternate crossing geometries includes ‘proximal’, ‘zig-zag’, and ‘distal’ crossings with varying offset distances of entry and/or exit crosswalk from the circulating lane. The modeled signalization options include one-stage and two-stage pedestrian-actuated control, as well as, the use of HAWK signals. The vehicle models for one- and two-lane roundabouts have been calibrated from NCHRP 3-65 data and will be used to conduct sensitivity analyses for a range of pedestrian and vehicle demands for the different scenarios. The results suggest that the impact of a pedestrian signal at roundabouts is greatest as vehicle volumes approach capacity, but that vehicle delay and queuing can be minimized through innovative signal configurations. The findings are important in light of recent discourse concerning the accessibility of roundabouts to pedestrians with vision impairments that may ultimately move towards a requirement for signalization for certain facility types.