The Effects of Countdown Signals on Intersection Capacity

This study presents the effects of countdown signals on the total start-up lost time of automobiles at signalized intersections based on the data collected at intersections in Bangkok, Thailand. This countdown signal is used to warn motorists in queue at the stop line during any red phase on when the green phase will be started. The data indicated that the countdown signals did not have any effects on the saturation headway of automobiles, but on the total start-up lost time. With the use of the countdown signals, the total start-up lost time was decreased from 4.3 seconds to 2.9 seconds, or was reduced by thirty-three percent. Therefore, the countdown signals may be used to increase the capacity of signalized intersections.