Real-world emissions of gaseous pollutants from diesel passenger cars using portable emission measurement systems

Passenger cars contribute significant emissions in urban areas affecting the air quality of cities. Traditionally, vehicular emission factors (EFs) were developed based on measurements in the laboratory. However, studies indicate that the laboratory measurements are unrepresentative of real-world conditions. In this study, EFs were developed for diesel passenger cars using Portable Emission Measurement Systems (PEMS) on urban arterials with heterogeneous traffic conditions in Chennai, India. Three diesel passenger cars from different manufacturers, of the same age, and complying with Bharat Stage IV (BS IV) emission standards were selected for emission monitoring. The results show that the average carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NOx) emission factors of the passenger cars were 1.28, 0.13, and 0.59 g/km, respectively. In addition, the measured EFs were influenced by the road type with higher emissions on roads with higher speeds and steeper accelerations. Finally, the total annual emissions generated by diesel passenger cars in Chennai city, for the current vehicle activity, were estimated to 7000 tonnes of CO, 750 tonnes of HC, and 2400 tonnes of NOx. Considering the increasing emphasis on electric mobility and public transport, this study provides a timely insight into emissions from diesel passenger cars.