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.
