Effect of Left-Turn Operational Mode on Pedestrian Safety

Pedestrian safety is a growing concern at signalized intersections. Pedestrians crossing a street at an intersection are exposed to interactions with turning vehicles, and these interactions sometimes result in crashes. Conflicts and crashes can be reduced by implementing protected turn phases. However, the inclusion of protected turn phases in a traffic signal cycle typically causes an increase in vehicular delay, which tends to offset the benefit of reduced crashes. The left-turn operational mode (permissive, protected–permissive, or protected) is typically chosen on the basis of vehicular traffic concerns such as volumes of left-turning and conflicting through vehicles, lane geometry, and sight distance. Historically, pedestrian safety has not been considered a factor in the selection of the left-turn operational mode. Pedestrian safety models have been calibrated with field data. The models allow pedestrian–vehicle conflict frequency and pedestrian compliance with signal indications to be estimated on the basis of volumes and site conditions. These models, along with vehicular delay analysis, form the basis for pedestrian-safety-based guidelines that were developed for choosing the left-turn operational mode. The guidelines are based on identifying threshold conditions for which a change in left-turn mode results in a reduction in road user costs.