In order to formulate rational traffic management measures for urban roads, it is essential to understand
the effect of different types of vehicle on congestion. The effect of different types of vehicle on
congestion has been captured on the basis of marginal congestion. Using congestion models, the marginal
congestions have been estimated for different road widths, traffic compositions and on-street parking
levels. The peak hour vehicular composition and volume level vary for different roads in an urban area.
Therefore, for assessing the operating conditions for different roads based on a comparable quantitative
measure, the marginal congestion caused per Passenger Car Unit (PCU) of mixed traffic stream has been
estimated and denominated ‘Marginal Congestion Index (MCI)’. The use of MCI for prioritization of
management actions for different urban roads is discussed. It is shown that a congestion model explicitly
accounts for the effects of traffic composition and volume level. Therefore, the effect of different types of
vehicles on congestion at all traffic volumes could be estimated using congestion models. Altogether,
modeling of congestion is established as a tool for formulating rational traffic management measures for
urban roads in developing countries.
