Exploring Impacts of Countdown Timers on Queue Discharge Characteristics of Through Movement at Signalized Intersections

Red signal countdown timer can show drivers the time remaining until the onset of the green phase. Drivers waiting in the queue at the intersection are aware of the upcoming green phase start, and are likely to respond more quickly. Thus, countdown timer can influence the queue discharge characteristics in green phase. This study investigates how countdown timer affects the queue discharge characteristics of through movement during the green phase. Headway data was collected by watching traffic surveillance video of two signalized intersections in GuangZhou before and after the countdown timers installed. It was found that countdown timer had an impact on the saturation headway, reducing it by 5% above, so did the standard deviation of the whole headways. That makes a 5% above increase in traffic capacity of through movement. However, the effects on the first vehicle to sustain saturation headway were found to be trivial.