Projection of passenger cars' air pollutants and greenhouse gas emissions and fuel consumption in Tehran under alternative policy scenarios

Passenger cars (PCs) are a major contributor to urban air pollution, greenhouse gas emissions, and energy security challenges in megacities in developing countries because of their high growth potential. Since the PC fleet changes through time, the projection of air pollutant emissions from PCs is essential for effective emission reduction policymaking. However, the extensive amount of data and proper models are required for this purpose that are not available in many developing countries. Hence, this study develops multiple econometric and emission models and integrate them into a framework to simulate the future stock and activity of PCs and projects PCs' air pollutants and CO2 emissions and fuel consumption in the megacity of Tehran by 2035. Various data treatments and estimations are used in response to poor transport-related data availability at the city-level. Eight alternative scenarios are considered to assess the effectiveness of different fuel consumption and emission reduction policies. Projections show that the PC stock will grow 70% by 2035 and reach 5.4 million while the activity level stays stable. Annual gasoline consumption of PCs passes 5.8 billion liters and CO2 and PM2.5 emissions elevate by 62% and 76%, respectively, under the business-as-usual scenario. Based on the results, implementation of stricter emission standards cuts 65% of gaseous emissions while promotion of compressed natural gas bi-fuel cars has no benefit in reducing air pollutants emissions. Cutting fuel subsidies is the most effective policy to limit PM2.5 and CO2 emissions, and fuel consumption growth by controlling the activity level of the fleet.