STUDY AND DEVELOPMENT OF BASIC RELATIONSHIPS FOR MIXED TRAFFIC FLOW

Abstract

The traffic stream in India as in other developing countries consists of two distinct categories of vehicles namely, fast mov-ing vehicles like cars, buses, trucks, autos, motor cycles and slow moving vehicles such as cycles, cycle rickshaws and bullock-carts. The static and dynamic characteristics of these two types of vehicles vary widely. Invariably the same right of way is used for the movement- of both types of vehicles. In this study the term <<mixed traffic" is used to denote a stream which consists of both slow and fast moving vehicles while in the context of developed countries this term represents the percentage of trucks and buses traffic i.e., commercial vehicles alongwith the passenger car stream. The Highway Capacity Manual, an authoritative document on highway capacity is silent on these aspects of mixed traffic. The effect of two wheelers i.e. scooters and motor cycles and presence of other slow moving vehicles in the stream are not considered in the Manual, and therefore, its application under mixed traffic conditions experienced by developing countries is very limited. The relationship among the basic parameters of traffic flow in context of developed countries is given by q = k.v. where each parameter has its standard value as per norms. However, this relationship is not applicable for traffic stream of developing countries where slow moving vehicles constitute a definite propor-tion in the traffic stream, therefore it suggests the need for an indepth study for development of the required relationship. It iv may be mentioned that this work for mixed traffic shall be appli-cable to homogenous traffic also. The various landuses are also of paramount importance for the movement of the traffic constituting different categories of vehicles in different percentages. Thus the composition of traffic is influenced and hence the parameters of traffic flow. The behaviour of the traffic being very intricate 9 the field studies have been conducted in a small town representing majority of two-lane two-way undivided roads in Indian towns and divided urban arterials in metropolis i.e. Delhi and Bombay. The conduc-ted study envisages different road widths and landuses. A computer programme incorporating different mathematical relationships was developed to predict a reasonable relationship:-between traffic stream parameters at different percentages of slow moving vehicles incorporating different statistical checks analysis of the data after validation proves that the relation-ships are acceptable to a greater degree of dependability. For the same type of roadway conditions and composition of traffic these relationships have a practical usage to a great extent, and have been presented in a generalized form and have been compared to a recently conducted World Bank Project (RUGS) results also.