Analysis of Driver and Pedestrian Comprehension of Requirements for Permissive Left-Turn Applications

Abstract

Operations engineers commonly program traffic signal controllers to serve the pedestrian movement at the same time as the parallel vehicular-through movement. This requires drivers completing a permissive left-turn movement to yield to opposing vehicles and pedestrians before selecting an appropriate gap. To minimize the potential safety problem, it is critical that drivers and pedestrians understand the permissive left-turn signal indications. The recently completed NCHRP Report 493 identified that a flashing yellow arrow (FYA) permissive indication provided a preferred alternative to the existing circular green permissive indication and recommended that the FYA permissive indication be included in the Manual on Uniform Traffic Control Devices. This paper presents research findings of a follow-up study that targeted the FYA impact on pedestrians, including driver comprehension of the need to yield to pedestrians and pedestrians’ recognition of appropriate crossing opportunities. Driver and pedestrian comprehension of the FYA indication was evaluated with a series of dynamic driving simulator evaluations and computer-based static evaluations. In total, 139 drivers and 100 pedestrians were evaluated in 5,930 experimental scenarios. The FYA permissive indication can be safely and effectively used at intersections with pedestrian activities. Given the high level of comprehension to yield requirements, the FYA is a recommended indication at T-intersections where pedestrian crossings are prevalent. Fewer than half the pedestrians understood correct crossing procedures when pedestrian signal heads were not present, and pedestrian comprehension of the walking requirements under a flashing “don't walk” were quite low in all scenarios evaluated.