Estimation of Passenger Car Unit (PCU) or Passenger Car Equivalent (PCE) of vehicles is the pre-requisite for highway capacity and level of service analyses and to formulate effective traffic regulation and control measures. Professional organisations in different countries have brought out guidelines for highway-capacity estimates for different categories of roads. The capacity estimate given in these manuals are, however, based on lane-based homogeneous traffic conditions and hence are not applicable for the highly heterogeneous traffic conditions prevailing in developing countries like India. This paper is focused on the estimation and study of the possible variation of Passenger Car Unit (PCU) values of different categories of vehicles at various traffic volume levels, under heterogeneous traffic-conditions prevailing on intercity roads in India. It has been found that the PCU value of a vehicle type varies considerably with variation in traffic volume. Hence, it may be appropriate to consider the PCU value of a vehicle type as a dynamic quantity instead of considering it as constant.