Three methods of PCU estimation at unsignalized intersections

Abstract

Estimation of passenger car unit (PCU) is a vital component of any traffic study conducted in developing countries owing to the heterogeneity in the vehicular traffic. Past studies on PCU factors are majorly limited to intercity and urban roads. However, PCU factors for different types of vehicles on unsignalized intersections have not been investigated so well. This paper presents three methods of estimating PCU factors for different types of vehicles on unsignalized intersections under highly heterogeneous traffic conditions. The first method is based on the occupancy time of a vehicle while clearing the intersection. The second method is based on the capacity of a priority movement estimated in terms of different vehicle categories. Queue clearance rate is used as the basis for PCU estimation in the third method. Data were collected at two unsignalized intersection in semi-urban area of two cities of India and PCU for different types of vehicles is determined using the three methods. The resulting values of PCU factors were found to be logical and are representatives of the actual field conditions.

Keywords:

• Passenger car unit
• unsignalized intersection
• occupancy time
• intersection capacity
• queue clearance rate

Acknowledgment

The work reported in this paper is the part of ongoing research project on ‘Development of Indian Highway Capacity Manual (INDO – HCM)’, sponsored by CSIR-CRRI, New Delhi. The financial assistance provided by the sponsoring agency for traffic studies is gratefully acknowledged.