Modeling Heterogeneous Traffic Flow

The composition of traffic in developing countries is mixed, with a variety of vehicles, motorized and nonmotorized, using the same right-of-way. The motorized or fast-moving vehicles include passenger cars, buses, trucks, auto-rickshaws, scooters, and motorcycles; nonmotorized or slow-moving vehicles include bicycles, cycle-rickshaws, and animal-drawn carts. The proportion of slow-moving vehicles in the traffic stream may vary from 10 to 80 percent. Since the 1950s, considerable research has been done to develop traffic flow models for roadways with mainly motorized vehicles or homogenous traffic, representing the composition of traffic primarily in industrialized countries. A review of the literature has shown that limited studies have been done to develop an understanding of traffic flow for non-lane-based heterogeneous or mixed traffic conditions in developing countries. Some efforts have applied a variation of practices developed for homogenous traffic by converting heterogeneous traffic to equivalent passenger-car units and then applying procedures for homogenous traffic. However, these efforts have produced mixed results. A comprehensive review is presented of the few studies on mixed, non-lane-based traffic in India, Bangladesh, and Indonesia. The unique characteristics of traffic composition, driver behavior, roadway geometry, maneuverability, and vehicular interactions are also presented. Most of the studies conducted in this area are not often readily available. This paper, therefore, should serve as a good reference.