Analysis and Estimation of Vehicular Fleet Emissions in the Islamabad City

Abstract

Air quality management and planning requires regular monitoring and accurate local emission estimates that are calculated on the basis of local conditions and controlling factors. To assess the contribution of light duty vehicles (including passenger cars, taxis, vans and motorcycles), to Islamabad‟s outdoor air quality, daily emissions were calculated with the help of IVE emission model. Results revealed a higher average age for these vehicles with taxis having an average age of 20.4 years and a significant share in overall pollutant emissions. Lower number of Euro compliant vehicles was also found during this study. Pre-Euro vehicles were found to be greatly responsible for higher emissions. Higher number of gasoline fueled vehicles was observed for each vehicle type (>80 per cent). Low engine stress modes (lower speeds with frequent decelerations) were observed for all vehicles especially on arterials and residential roads. This can be attributed to the rapid increase in vehicle population, ongoing construction of a mass transit bus project in the city, diversions and partially blocked roads for security purposes, and higher number of traffic signals. Highest overall emissions (59 per cent) were observed on arterials, followed by residential roads (24 per cent) and highways (17 per cent) with higher emissions observed during morning (8-10 am) and evening (4-6 pm) hours. Consequently, composite emissions factors were calculated and used to estimate annual emission inventory for Islamabad. Results showed that annually, 1093 kt of CO2, 147 kt of CO, 18.5 kt of VOCs and 11 kt of NOx were emitted by light duty vehicles during the year 2014.