Improving Pedestrian Progression at Multistage Crossings Using Pedestrian–Left Turn Overlaps

Abstract

At signalized intersections where pedestrian crossings are divided into two stages by using a median island, pedestrian delay can be very long if the partial-crossing phases have poor progression. One technique for reducing pedestrian delay is pedestrian–left turn overlaps, in which half-crossings that are not in conflict with a left turn are allowed to run during the left turn phase as well as during the parallel vehicle through phase. Such an overlap can enable some pedestrians to cross in a single pass, or to have a far shorter wait at the median. Because this technique requires surrendering some of the flexibility with which left turn phases normally operate—in phases with a pedestrian call, the left turn phase cannot be skipped and may require a longer minimum green—there can also be an impact on vehicle delay. A case study of two intersections in Brookline, MA found that, compared with the current timing plan, using pedestrian–left turn overlaps could reduce pedestrian delay from about 100 to 35 s, with a negligible impact on vehicle delay. A methodological innovation introduced in this study was that average pedestrian delay was calculated for three pedestrian speeds and averaged together, thus accounting for how pedestrian delay at multistage crossings can be far lower for faster pedestrians who may be able to cross in a single pass than for slower pedestrians who have to wait at the crossing island.