Real time roadway pollution in Indian cities: A comparative assessment with modelled emission

Abstract

Roadway transport sector is one of the major contributors of atmospheric pollution. The study aims to understand the real time roadway pollution in megacities and medium sized Indian cities; therefore, the present study estimated on-road emission factors (EFs) and compared them with two other regulatory models for Delhi and Guwahati. Both the cities are different in traffic flow management strategies, traffic composition and vehicular density per 1000 population. Emission rate was found higher in Guwahati (17% to 38%) due to frequent stops-and-go patterns of driving profile and poor traffic flow management per vehicle as compared to Delhi, but overall roadway pollution load is higher in Delhi due to higher vehicular density. The real-time on-road EFs were compared with modelled EFs, estimated with two regulatory models International Vehicle Emission (IVE) model and COPERT-IV. The modelled EFs magnitude is lower than the real-time EFs. Pollutants HC, CO and CO2 were about 17% to 30% and 33% to 55% fewer from IVE and COPERT-IV respectively whereas NOx emissions are over predicted by both the models (COPERT-IV: -54% to -95% and IVE: -26% to -35%). Results demonstrate that efficient traffic flow management plays important role in reducing roadway pollution, which is major share of environmental pollution, but uncontrolled vehicular growth quickly offsets the benefit of emission control policies. Therefore, there is need for establishing equilibrium between emission control and vehicle growth rate in control policies for optimum benefits from policies for each city.