Research on Numerical Simulation of Pollutant Dispersion at Expressway Toll Plazas Based on Multi-Influencing Factors

Currently, expressway toll stations in China generally use loading-based toll collection. Because vehicles spend long time either stationary or accelerating/decelerating in low gears, air quality is particularly susceptible to the accumulation of vehicle-emitted pollutants at toll plazas. In this work three-dimensional computational fluid dynamics (CFD) simulations were carried out to analyze the pollutant concentration distribution in the vicinity of tollbooths. Several influencing factors including wind velocity, wind direction and topography of toll plazas were considered. A simulation instance of the Wuzhuang toll plaza in Hefei-Nanjing expressway was performed. The simulation results show that the increase in wind speed facilitates the pollutant dispersion. There is higher concentration of pollutant as the angle between the direction of wind and traffic becomes larger. The existence of retaining walls impedes the pollutant dispersion. However, the slope of retaining walls has little influence on the variation of pollutant concentration.