Validating Area Occupancy–Based Passenger Car Units and Homogeneous Equivalent Concept under Mixed Traffic Conditions in India

Abstract

This research work puts an emphasis on passenger car unit (PCU) estimation using different methods on eight-lane divided urban multilane roads using a well-calibrated and validated microsimulation model. In this context, at first, three methods were applied for PCU estimation and were checked for its accuracy, which are: (1) PCU estimation using the TRRL (Transport Road Research Laboratory, UK) definition; (2) PCU estimation using the speed–area ratio concept; and (3) PCU estimation using a newly proposed methodology in this study, which is based on an area occupancy–based matrix solution of simultaneous equations developed between a mixed-traffic scenario and an all-cars traffic scenario. The PCU equivalent flow using three methods, compared with the all-cars scenarios at different flow levels, resulted in mean absolute percentage errors (MAPE) of 6%, 12%, and 7%, respectively. Subsequently in this study, a new concept of homogeneous equivalent is also proposed, which directly converts heterogeneous flow into a homogeneous equivalent using the area occupancy value of a mixed-traffic stream. The concept is tested over varying traffic compositions and different traffic volumes and resulted in a MAPE of 8 to 18%. The output from the present study may be useful to traffic engineers, researchers, and practitioners for getting equivalent flow on different uninterrupted facilities, using this simplified yet scientific methodology.