An Approach to Tackle Urban Congestion and Vehicle Emission by Manipulating Transport Operations and Vehicle Mix

Abstract

Emission from motorized vehicles is a major source of air pollution in urban areas. However, it varies significantly with vehicle technology, type of fuel used, operating conditions, vehicle mix, etc. Understanding the relationship amongst congestion levels in terms of Level of Service (LOS) policies, emission levels and traffic compositions is important for effective policy development for pollution reduction. This study adopted an integrated optimization model to understand this complex relationship with the help of suitable performance indices considering total emissions, fuel consumption, vehicle delays as well as capacity utilization of an intersection in Kolkata, India. SYNCHRO, a transportation operational analysis program is used to develop all the possible LOS thresholds. Twelve different traffic compositions are considered by modifying the share of vehicle categories. Emission inventories are generated using MOBILE, SYNCHRO and CRRI methods of emission calculation. To validate the emission inventories developed from these models, concentrations of the two major pollutants, Suspended Particulate Matter (SPM) and Oxides of Nitrogen (NO_x) are collected from the intersection site using High Volume Air Sampler. Estimation of emission for base case by MOBILE yielded closest results with that of actual emissions estimated by the High Volume Air Sampler at the site. While comparing the performance indices, for the Kolkata intersection, LOS B is found to be the most effective operating point for combined emissions, fuel consumption and traffic congestion (delay at the intersection) point of view. There is also evidence that reduction in emission is associated with decreased share of motorcycles.