Quantification of reduction in air pollution due to bypassing traffic in Delhi, India

The worldwide known relationship between transport and air pollution is demanding innovative solutions for satisfying the mobility needs with minimum pollution. While reducing the mobility demand is a longterm target, the most commonly adopted approach is to decongest the ‘hot spots’ having an alarming level of pollution. The main objective of providing bypasses and expressways is to divert the through traffic coming into the city. Delhi is one of the most congested and polluted cities in India. Among the various sources, vehicular pollution is a significant source of air pollution. Different policies and strategies have been developed to decongest and depollute Delhi. The Eastern Peripheral Expressway (EPE) is one such option implemented to decongest the national capital of India by diverting the traffic not destined for Delhi. It becomes essential to evaluate the performance of such significant infrastructural investments for better decision making in the future. Accordingly, the present study quantifies the impact of constructed EPE in terms of diverted traffic and the reduction of vehicular pollution from the capital of India. For this, various primary surveys like classified traffic volume, origin–destination and fuel station surveys were conducted in the study area. Vehicle kilometre travelled for all vehicle types was calculated using the primary data, and this parameter is considered for quantifying vehicular emissions. The results showed that reduction of vehicular emission due to diverted traffic was 0.7% of PM (PM_2.5), 7.1% of NO_x and 2.5% CO in the total vehicular emission load of Delhi.