Modeling impact of vehicular emission management strategies on air quality

Traffic induced pollution is currently one of the major problems in urban areas in India. The Government of India has proposed several action plans and emission control strategies for pollution abatement like change of fuel in public vehicles from diesel to CNG, phasing out of older vehicles and new emission norms like EURO III and IV. Though these strategies are beneficial per se, however there is a need to develop a rational method or objective decision making tool to test or evaluate the impact of these strategies. Prediction of air pollution concentration through mathematical models, its mapping and assessment of environmental impacts is needed for this purpose. Hence, this paper presents an integrated package which consists of an emission model, a dispersion model and a feedback control loop which has been applied for evaluating alternate emission management strategies.

The methodology involves development of emission model which calculates the line source strength specific to Indian conditions. The model takes classified vehicle count data and classified vehicle emission factors as inputs for a particular road link. Average speed dependent emission factors are built into the model. These emission factors are also based on vehicle technology, fuel, age and emission norms. They represent Indian driving conditions and Indian driving cycle. The model is developed by taking values of emission factors from previous studies done in India and in other countries and incorporating certain changes to specifically represent Indian traffic conditions. A micro range domain like an intersection and a freeway is selected to apply the model. The outputs of the emission models are used as inputs to air quality dispersion models like CALINE or ADMS to predict the concentration of pollutants at certain receptors for a given set of meteorological conditions. The emission and dispersion models are validated and verified with field or laboratory scale studies. Firstly, the model package is operated for “Business As Usual” scenario. Then it is used to evaluate different management strategies, so that the most effective one can be implemented.