Estimation of Passenger Car Unit on urban roads: A literature review

Passenger Car Unit (PCU) is a relative weightage factor given to the traffic volume of individual vehicle category to deal with the heterogeneity in a mixed traffic situation. Ample volume of studies was conducted till date to estimate PCU of different vehicle categories. This paper discusses the methodologies adopted in these studies for estimation of PCU and analyses the advantages and limitations of each method. A number of researchers proposed static values of PCU while some of them realized its dynamic aspects. These studies also examined how PCU is changing with traffic characteristics, road geometrics and other factors. The present review found that PCU recommended in literature are region specific (traffic characteristics and driving culture vary across nations) resulting in high inconsistency in the outcome. Inconsistency was found not only in the range of PCU but also in the trend how it is varying with other governing factors. This paper provides a categorical summary of the research outcome in the domain of PCU estimation on urban roads.