Impact of real-world traffic and super-emitters on vehicular emissions under inter-city driving conditions in Maharashtra, India

Motor vehicles emit particles and other gaseous pollutants that adversely affect human health and the climate. This study investigates the impact of traffic characteristics on vehicular emissions under real-world inter-city highway driving conditions by examining vehicles that release disproportionately high level of air pollutants (super-emitters). Real-time pollutant concentrations from a heterogenous traffic fleet were measured at the entry and exit of Kamshet-I roadway tunnel, located on Mumbai-Pune Expressway. Vehicles with visible plume of smoke and overloaded vehicles (grouped as super-emitters) were visually identified. The average hourly traffic of 1560 (+/- 410) vehicles at an average speed of 78 (+/- 4) km.hr(-1), composed of similar to 80% light duty vehicles (LDVs) and similar to 20% heavy duty vehicles (HDVs). Concentrations of all the measured gaseous and particulate pollutants at the exit were up to 2.5 times higher (p < 0.05) at the entry. Super-emitters accounted for one-fifth of the total fleet and were significantly associated with fine particles (R = 0.71). Developed statistical prediction model for super-emitters showed the influence of vehicle age for LDVs, and both vehicle age and overloading for HDVs. These findings can inform future vehicle regulation policies to systematically reduce emissions from super-emitters, by targeted vehicle inspection programs and retrofit initiatives toward reducing air pollution in Indian cities.