EFFECT OF COUNTDOWN DISPLAY ON QUEUE DISCHARGE CHARACTERISTICS AT SIGNAL CONTROLLED INTERSECTIONS

Abstract

Intersections are the bottlenecks in the urban roadway network and are critical determinant of transport system's capacity, performance and safety. Signal-controlled intersections are those which are governed by traffic signals for the movement of vehicles. Two types of signal controlled intersections namely with timer and without timer are predominantly present on urban roads. Countdown display at signal controlled intersection are getting popular in many cities like New Delhi. Passenger car units is a paian1etcr which converts heterogeneous traffic flow into homogeneous traffic. PCU is useful in detcnnining the capacity of roads. Previous studies indicate that standard PCU as suggested by codes/manuals do not hold good at signal controlled intersections. In this study, the intersection is located on Lodhi road and beeshma pitamah inarg near Dyal Singh College in New Delhi was selected as the study location based on the ease of access to obtaining the data. Traffic data was collected for 6 hours, in which three hours were during the condition where signal timer was in operation and the remaining three hours were when the timer was turned off. Each three hour traffic data was collected at same time of two different days to replicate the effect of traffic volume. Two cameras of high resolution were used to collect the video data, with one camera focusing the traffic stream and the other capturing the traffic signal. Most of the studies report that saturation headway starts from 4Lh or 5" vehicle in the queue which does not holds good in heterogeneous traffic conditions. The headways in with timer condition are less than the headways in without timer condition. This results in increase of the traffic flow during with timer condition. The minimum headway observed was in the range of 1.2 to 2 seconds, which is slightly lower than the existing 14CM value of 1.9 seconds. PCU values ot'all vehicle categories decreased from with timer condition to without timer condition. During with timer condition, it has been observed that vehicles tend to maintain closer headways than in without timer condition as they have the advanced information of the signal indication. Saturation flow was observed to slightly reduce during without timer condition when compared to that of timer condition.