Investigating the influence of traffic emission reduction plans on Tehran air quality using WRF/CAMx modeling tools

Abstract Due to its dangerously high level of pollutants, Tehran air quality is a serious concern. Several immediate and emergency solutions have been pursued to mitigate the problem in the short term. Most of the solutions are based on traffic-restriction schemes that pose challenges to citizens’ mobility. As part of such policies, the central part of the city has been converted into a traffic restricted zone (TRZ) in which vehicles are allowed to enter only on certain days of the week based on their license plate number. The purpose of this study was to investigate the effectiveness of such policies on reducing the concentration of various pollutants by using advanced air quality modeling approach. First, the pollutant emissions were calculated using the International Vehicle Emissions (IVE) model, and the results were used in the WRF/CAMx modeling system to investigate the effects of traffic restriction enforcement policy on air quality and pollutants dispersion over Tehran. Measured data at monitoring sites were used to benchmark performance of the modeling system. The results showed satisfactory performance of both models in predicting meteorological parameters and concentration of pollutants. While emission input data was reduced by 40% in the TRZ, the maximum reduction in CO as a primary pollutant was approximately 20%, which is highly related to the traffic conditions. Results suggest that effectiveness of TRZ policies highly depends on the type of pollutant, meteorological conditions, and the location of the study area.