DYNAMIC PCU AND ESTIMATION OF CAPACITY OF URBAN ROADS

This paper presents a concept of 'dynamic passenger car unit' ('dynamic PCU'), appropriate for the heterogeneous traffic on Indian roads, and shows that the PCU factor for a vehicle type is not a static factor as is usually assumed. This PCU factor is the ratio of the projected rectangular area of the vehicle type, as a proportion of that of a car, to the velocity of the vehicle type, as a proportion of car velocity. The velocities for different vehicle types are found by solving a set of linear simultaneous equations, whose coefficients depend on: (1) traffic stream composition; (2) the road's total mixed traffic flow per unit time; (3) total carriageway width; and (4) parameters to be estimated by linear regression analysis. Variations of dynamic PCUs are plotted, in relation to traffic composition, for a section of the Delhi Ring Road, for the following vehicle classes: (1) car/jeep/taxi; (2) bus/minibus/truck; (3) motorised three-wheeler; (4) motorised two-wheeler; and (5) bicycle. Speed-flow relationships and road capacity estimates are also discussed.