Review of Studies on Mixed Traffic Flow: Perspective of Developing Economies

The traffic scenario in developing economies is fundamentally different from that of the developed economies. The latter is predominantly composed of passenger cars and can be aptly termed as "homogeneous'' traffic, whereas the former is composed of vehicle types with a wide variety of static and dynamic characteristics, which occupy the same right of way, resulting in an unsynchronized movement of the vehicles. Another distinguishing characteristic of this traffic is the absence of lane-discipline, resulting from the wide variation in sizes and maneuvering abilities of the vehicles. These distinctions result in some phenomena like vehicle creeping, which are absent in the homogeneous traffic. Hence, this type of traffic can be referred to as "heterogeneous disordered'' or "mixed'' traffic. A review of the literature has shown that most of the studies in such traffic make use of the methods and concepts developed for homogeneous traffic. Very few studies have attempted to capture and understand the distinctive characteristics of the mixed traffic. The primary objective of this paper is to provide a review of the studies on various mixed traffic characteristics in developing economies, identify their limitations and provide guidelines for the future research. Also, a detailed methodology of the simulation process for the mixed traffic is given, reflecting the "gap-filling'' rather than the conventional "car-following'' behavior. A comparison of the past modeling approaches is also presented and the accuracy of their implementation is discussed.