The Effects of Pedestrian Countdown Timers on Safety and Efficiency of Operations at Signalized Intersections

Pedestrian countdown timers are becoming common at urban and suburban intersections. The added information that pedestrian countdown timers provide to pedestrians can also be used by approaching drivers. A before-and-after case study on the effects that pedestrian countdown timers have on safety and efficiency of operations was performed at two signalized intersections in Lincoln, Nebraska. The effects on both drivers and pedestrians were analyzed. Performance measures for pedestrian analysis include pedestrian compliance and average pedestrian walking speed. Performance measures for the driver analysis include probability of stopping and speed gain of vehicles at the stop bar during the yellow phase (vehicles passing through the intersection during the yellow phase) and queue discharge headway. Data was collected using a Wide Area Detector (WAD), point detector at the stop bar and a Pan-Tilt-Zoom (PTZ) video camera. Data was collected using state-of-the-art data collection software, Wonderware, which displayed all traffic and pedestrian signal information, vehicle detections, individual vehicle speeds, vehicle distances from stop bar, and the video from the PTZ camera all on one computer screen. Statistical models were estimated to understand the effects that pedestrian countdown timers have on the performance measures. The resulting models identified statistically significant factors that affected the performance measures. Pedestrian countdown timers were found to increase pedestrian walking speed by 0.2 ft/sec, and decrease the probability of pedestrian violations. Impact of PCT on driver safety and efficiency was not found to be statistically significant at 95% level of confidence. There was however some evidence, although not statistically significant of improvement of driver safety due the presence of PCT. The trend was more pronounced at the intersection of 17th and G (smaller intersection with less visual clutter) where the authors observed reduction in the percentage of red light runners and some reduction of dilemma zone boundaries.