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, the countdown timer can influence the queue discharge characteristics in green phase. This study investigates how the countdown timer affects the queue discharge characteristics of through movement during the green phase. Headway data were collected by watching traffic surveillance video of two signalized intersections in GuangZhou before and after the countdown timers were installed. It was found that the countdown timer had an impact on the saturation headway, reducing it by above 5%, as it did on the standard deviation of the whole headways. That makes an above 5% increase in traffic capacity of through movement. However, the effects on the first vehicle to sustain saturation headway were found to be trivial.