Whilst the developed nations have used technology-forcing standards or market mechanisms (such as taxes) as their main tool for the control of transport pollution, transportation demand management (TDM) may have greater relevance for cities in poorer countries: and the choice of less polluting modes of travel is a crucial aspect of TDM.

We measure, for the city of Kolkata (India), the degree of pollution (considering the five most major pollutants) by all existing modes of transport and the total air pollution created due to the present modal structure. With the help of a carefully selected sample of 3000 individuals residing in and/or commuting to the city, we determine the extent to which we can make transport users shift to less polluting modes, and hereby evolve a number of feasible modal structures that would reduce air pollution. We thus determine the benefit (in terms of emissions reduction) and costs of changing the current modal structure to each of these alternatives. We are hereby able to arrive at the optimum modal composition.