Evaluating Safety Impact of Countdown Signal Timers at Signalized Intersections

The primary objective of this study is to evaluate the impact of countdown signal timers on the safety of signalized intersections .Data were collected at 13 approaches of 9 signalized intersections .A cross-sectional analysis was conducted to compare the safety performance of signalized intersections with and without countdown timers .Various sur-rogate safety measures ,such as the red-yellow running violation ratio and traffic conflicts ,were used for safety assess-ment .It is found out that the countdown signal timers significantly increase the red-yellow running violation and traffic conflicts at signalized intersections for both through and protected left-turn movements .The study results of this paper suggest that the countdown signal timers negatively affect the safety performance of the signalized intersections and there-fore ,should be used more cautiously .