Effect of Countdown Timers on Traffic Characteristics and Driver Behaviors at Signalized Intersections
Signal countdown timers are being installed adjacent to the traffic signal heads at major signalized intersections in India. These timers display the seconds remaining for a particular signal phase to the drivers and expected to help them with a better decision making process. Conflicting results have been obtained by researchers across the world regarding timers' effect on the efficiency and safety potential at signalized intersection locations. Therefore, the present study tried to assess the influence of timers on several traffic characteristics and driver behaviors by collecting data from three signalized intersection locations in New Delhi. Total of three different approaches were studied both in the presence and absence of timers. It was found that the timers did not influence saturation flow, but they helped reducing the start up lost time significantly. Percentage of cycles with red light violations (RLVs) and mean RLV per RLV cycle increased in the presence of timer during the last 10 seconds of red phase, but different effect was observed for RLVs that took place during the initial 10 seconds of red. Drivers started moving from their position during the final stage of red phase resulting in more number of violations during timer on scenario. On the other hand, timers assisted drivers make better decision regarding stopping or crossing the intersections at the end of green, thus reducing violations during the initial stage of red phase. Timer off scenario enlarged total ranges of both Type I and II dilemma zones at the onset of yellow and brought Type II dilemma zone earlier.