Examining some potential actions in mitigating gaseous emissions from vehicles,case study: Tehran

Pollutant emission from vehicles is known as a major air pollution source in metropolitan areas. Efficiency of several solutions was quantified and compared to introduce the best solution for decreasing greenhouse gases and air pollutant emissions: (1) inspection and maintenance (I/M) of vehicles, (2) restriction of air conditioner usage, (3) injecting better quality fuel (removing sulfur), and (4) replacing older vehicles with new ones were modeled by International Vehicle Emissions (IVE) model as potential solutions. Restricting air conditioner usage makes an insignificant contribution in pollutants’ emission. The idle inspection/ maintenance system can reduce carbon monoxide (CO) and methane (CH ₄) emission by about 10.7 and 3.8 %, respectively. The loaded I/M system reduces nitrogen oxides (NO _x ), CO, volatile organic carbon (VOC), and CH ₄ emission by 8.6, 11.5, 3.4, and 7.6 %, respectively. Effect of I/M programs depends on the types of vehicles and target pollutants needed to be reduced. Sulfur emission into the atmosphere would be reduced remarkably (about 98 %) if its concentration was reduced in fuels. Substitution of old vehicles with new vehicles makes a noticeable contribution in improving air quality (about 53 % reductions in CO, 52 % in VOC, and 58 % in CH ₄ emission for light-duty vehicles). Analytical hierarchy process (AHP) was utilized to identify the most feasible solution for reducing air pollution. Fuel quality improvement and replacing old cars with newer ones are the most tangible solutions, respectively. This paper demonstrates that each policy has its own impact on emission and we can apply each of them in cases in which the pollutants concentrations are high.