Exploring the Pattern of Platoon Dispersion Caused by Traffic Signal

Platoon dispersion is an essential phenomenon to be studied for determining the traffic arrivals at downstream intersections to access the need for signal coordination and to optimize the signal timing plans in coordinated signal systems. However, platoon dispersion is difficult to determine compared with other traffic flow parameters such as traffic volume, saturation flow, and speed. This paper explores the pattern of platoon dispersion caused by traffic signal, in which the focus are given on vehicle headway, intra-platoon headway and inter-platoon headway. Field investigation was made by means of videotapes which record traffic flows at selected location at Senai, Johor. After processing the data, vehicle headway at several consecutive points downstream of traffic signal were obtained and used for the platoon dispersion analysis. The dispersion patterns obtained from the observation during peak and off-peak periods were fitted with the theoretical distribution models. It was observed that vehicle headways follow the Erlang and Shifted Negative Exponential Distribution, intra-platoon headways have Normal Distribution and inter-platoon headways do not fit the tested distribution model.