DETERMINATION OF EQUIVALENT HOMOGENEOUS TRAFFIC FLOW IN RELATION TO ROADWAY OCCUPANCY

Abstract

To make the capacity-analysis feasible, the normal procedure is to homogeni.ie the mixed traffic in terms of a common vehicle. For this purpose different types of vehicles having widely varying sizes, speeds and manoeuvrability have been expressed in terms of a common design-vehicle-unit, viz., passenger-car. Certain values of passenger-car-equivalency-factors (commonly known as Passenger-Car-Units or PCUs) for different types of vehicles have been suggested by various agencies in India,and abroad too.,- based upon the relative speed of vehicles in the flow, physical dimensions or congestion indices and densities, and overall levels of service. Certain constant values of such equivalency factors. can be adopted only tentatively till more rational values, dependirg upon their relative interference values in a traffic stream under ,prevailing roadway and traffic conditions, are evaluated. For a given roadway conditions, the prevailing traffic conditions are subject to variations in time-space domain. It clearly brings out that the equivalency factors must be susceptible to changes in traffic conditions and thus, their constant values lose much of their meaning, as the deterministic values do not have a built in corrective mechanism. The study, presented here, suggests an approach to determine passenger-car-equivalents (PCEs) which are sensitive to traffic conditions on a prevailing Broadway.