OVERTAKING BEHAVIOUR ON A TWO-LANE ROAD

Abstract

Two-lane roads in India (64% length of NH and more than 50% length of SH) share a very large proportion of traffic. On Indian roads, size, width, speed and operational characteristics vary greatly from one vehicle to another. Individual interactions with other vehicles demand a unique decision-making process. Simulation model is used by the highway designer and practitioner to measure and evaluate traffic design and operations information regarding the performance of two-lane highways. In the present study the arrival pattern, speed distribution of different types of the vehicles, acceleration rates of the different vehicles during overtaking maneuver and overtaking time taken by the vehicles are investigated from the field data obtained on different sections of National Highways and State Highways of India and are used to develop a simulation model, to represent the traffic flow on a two-lane road. The simulation model has been coded in `CF+' language for processing on a high speed digital computer. The model is capable of incorporation five categories of vehicles, viz., car, heavy vehicles, two-wheeler, auto rickshaw and bicycle. The performance of the model has been validated on macro level by obtaining the capacity of a two-lane road and comparing the same with the literature. Simulation runs are performed at different flow levels and for mixed traffic consisting of two types of vehicles including passenger cars and any one of the remaining four categories of vehicles. In a mixed traffic condition, the fast moving vehicle are greatly influenced by the presence of slow moving vehicles with substancial reduction in the operating speeds. The variation in volume also changes the operating conditions to a certain extent. The change in the average stream speed was studied at a constant traffic volume and varying percentage of second category of vehicle in a stream of cars. The effect on the capacity due to presence of any of the four types of vehicles on a stream of cars was analyzed and the Equivalent Factors based on number of overtakings were also calculated.