New Approach for Estimating Passenger Car Units on Multilane Urban Roads with Heterogeneous Traffic Conditions

Abstract

This paper illustrates a newly developed methodology for passenger car unit (PCU) estimation under non-lane–based heterogeneous traffic conditions on multilane urban roads, using area occupancy as a measure of performance. The results show that an increase in the number of lanes or in carriageway width has a significant increasing effect on PCU values of vehicle categories. To examine the accuracy of the proposed method, speed–flow plots are compared on same set of axes using (1) the proposed unique (optimized) PCU values, (2) a dynamic set of PCU values (estimated using the common speed:area ratio method under non-lane–based traffic conditions), and (3) a static set of PCU values from existing guidelines, at a 5-min interval aggregation level for selected roads using real field data. The comparison shows a difference of 2. and 1.3% at capacity level for eight-lane divided and ten-lane divided road sections, respectively. This ensures the accuracy of the proposed simplified yet rigorous methodology of PCU estimation as well as the proposed unique set of PCU values. The soundness of the developed unique/optimized PCU values is checked on a test section of an eight-lane divided road having similar roadway and traffic conditions. At the capacity-flow level, the error is well within acceptable limits (.3–3%), indicating the credibility of the developed matrix-based PCU method using area occupancy as a measure of performance.