Passenger Car Unit (PCU) : Practically, the passenger car is considered as standard vehicle unit to convert the other vehicle classes and this unit is called ‘Passenger Car Unit’ or ‘PCU’.

Factors affecting PCU values:

The PCU values of different vehicle classes depends upon following factors:

1) Dimensions of vehicles such as width and length.

2) Dynamic characteristics of vehicles such as power, speed, acceleration and braking.

3) Transverse and longitudinal gaps or clearance between moving vehicles which depends upon the speeds, driver characteristics and the vehicle classes at the adjoining spaces.

4) Traffic stream characteristics such as composition of different vehicle classes, mean speed and speed distribution of the mixed traffic stream and volume to capacity ratio.

5) Roadway characteristics such as road geometrics including gradient and curves, access controls, rural or urban road, presence of intersections and the type of intersections.

6) Regulation and control of traffic such as speed limit, one way traffic, presence of different traffic control devices etc