Determination of Dynamic Passenger Car Unit for Heterogeneous Traffic: A Case Study of a Multi-Lane Divided Highway in Nepal

https://doi.org/10.46610/JoTS.2026.v011i03.005

Abstract

Nepal’s traffic is characterized by highly heterogeneous, non-lane-based traffic, where different vehicle categories interact with the same roadway space. The use of constant Passenger Car Unit (PCU) values under such conditions may not adequately represent the dynamic effects of vehicle characteristics and prevailing traffic conditions. This study determines Dynamic Passenger Car Unit (DPCU) values for major vehicle categories under heterogeneous traffic conditions. The study selected a 54m straight mid-block section of the four-lane divided Araniko Highway between Sallaghari and Chundevi. Videographic surveys were conducted over four days: three consecutive days and an independent day two weeks later, with observations during morning, afternoon, and evening periods. DPCU values were estimated using the Modified Homogenization Coefficient Method, considering the relative operating speed and roadway space occupancy of each vehicle category with respect to passenger cars. Temporal stability was assessed using the coefficient of variation, while independent validation was performed using the Absolute Percentage error. The final DPCU values were 0.23 for two-wheelers, 1.12 for utility vehicles, 1.47 for mini trucks, 2.98 for buses, and 3.01 for trucks, with passenger cars as the reference vehicle (DPCU=1.00). The proposed values can support traffic volume conversion, capacity analysis, and highway planning and design for multi-lane divided highways under similar conditions.