An empirical analysis of the effect of pedestrian signal countdown timer on driver behavior at signalized intersections

A pedestrian countdown signal (PCS) is designed to provide additional information to pedestrians at crossings and help their crossing decisions. However, the PCS information can also affect drivers' behaviors when it is visible to drivers. With the countdown information visible to drivers, they can know the timing of the onset of the upcoming yellow and red traffic lights. This unintended information might cause changes in driving behaviors such as early stops, speeding, or abrupt accelerations to cross an intersection before the red light. Current literature has mainly focused on the drivers' crossing decisions or the number of crashes before and after displaying a PCS at intersections. However, there is a paucity of studies that investigate drivers' behaviors when approaching signalized intersections equipped with a PCS. This paper investigates vehicle speed patterns, safety implications, and the factors influencing driving behaviors at intersections before and after displaying the countdown information. To do so, we collected and extracted video-based vehicle trajectory data from 5,000 vehicles at signalized intersections with and without a PCS in the City of Montreal, Canada. The observed data provide the median and 85th centile approaching speed, the intersection entering speed, as well as safety implications regarding the countdown information. The multilevel mixed-effect model and Tukey's test conduct statistical comparisons across intersections and signal phases. The study results demonstrate that drivers cross intersections at a higher speed when the pedestrian countdown information is visible to drivers. Moreover, the vehicles at the same intersection with a PCS show clearly different speed patterns before and after the onset of the countdown timer. After controlling other factors, the mixed-effect model results further indicate displaying a PCS to drivers increase the approaching speed by approximately 11 km/h.