Road traffic flow and air pollution concentrations: evidence from Japan

Vehicular emissions are a major global health concern. The aim of this study is to examine the short-term relationship between road traffic flows and air pollution concentrations in Japan. Our approach involves matching hourly data from the 2015 Road Traffic Census to data from nearby air pollution monitoring and meteorological stations and estimating a dynamic panel model. We focus on four pollutants designated under the vehicle emission standards of Japan: nitrogen oxides (NOx), carbon monoxide (CO), nonmethane hydrocarbons (NMHC), and fine particulate matter (PM_2.5). The standard estimates indicate that short-run pollution concentration-road traffic flow elasticities are 0.04–0.05 for NOx, CO, and NMHC, and insignificant for PM_2.5. Long-term effects are also estimated. We apply the estimates to a case study on the link between road traffic flows and meeting the new World Health Organization air quality guidelines.