Heterogeneous Impacts of Local Traffic Congestion on Local Air Pollution within a City : Utilizing Taxi Trajectory Data

This study estimates causal effects of traffic congestion on air quality in local areas within a city, highlighting spatial variations in local traffic, local air pollution, and health risks to residents due to local pollutant exposure. We employ a large size taxi driving trajectory data to construct measures of traffic congestion in local areas surrounding air quality monitoring stations in Beijing, at hourly basis. The station-by-hour panel data enables estimation of both contemporaneous and lagged marginal effects of local traffic on local air pollution. We find that local traffic congestion increases concentrations of NO2 and CO contemporaneously, but concentrations of PM2.5 and PM10 (which are largely secondary pollutants) in a two-hour lagged manner. The magnitude and significance of these effects vary with local traffic and pollution conditions. These results highlight the importance of evaluating environmental and health benefits of traffic policies at local area level