Abstract: 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 .