INFLUENCE OF TRAFFIC MIX ON PCU VALUE OF VEHICLES UNDER HETEROGENEOUS TRAFFIC CONDITIONS

Abstract

Study of the basic traffic flow characteristics like traffic volume is a prerequisite for the effective planning, design, operation and management of roadway systems. Traffic in developing countries like India is heterogeneous in nature, consisting of vehicles of different categories with widely varying dimensional and operational characteristics. The moving vehicles of heterogeneous traffic occupy any convenient lateral position on the road without any lane discipline, based on the availability of space. The interaction between moving vehicles under such traffic condition is highly complex in nature, which can be represented in terms of the amount of impedance caused to flow of traffic by a vehicle type in comparison with that of standard vehicle (passenger car). Passenger Car Unit (PCU) can be an appropriate measure to represent the relative impedance caused by a vehicle in heterogeneous traffic. This paper is concerned with the application of micro-simulation techniques to derive equivalency values (PCU factors) on a purely homogeneous (cars-only) traffic stream as well as on a heterogeneous traffic stream for different categories of road vehicles over a wide range of traffic flow and compositions on four-lane divided urban roads in India. The PCU values obtained for the different types of vehicles, for a wide range of traffic volume and composition, indicate that the PCU values of a vehicle type significantly changes with change in traffic volume and composition.