The effect of exhaust emissions from a group of moving vehicles on pollutant dispersion in the street canyons

Abstract

Moving vehicles are the primary emission source of road pollution and the vehicle-induced turbulence (VIT) affecting the flow field in the street canyon. This paper used the dynamic mesh updating method to simulate the air pollution under the real situation of vehicle movement and exhaust emission in the street canyon. The dispersion characteristics of vehicular exhaust under various vehicle arrangements were analyzed. The personal intake fraction (P_IF) was introduced as an index to analyze the impact of factors such as vehicle speed and ambient wind velocity on the pollution exposure level of pedestrians. Based on the general assumptions in the study of street canyon pollution that vehicle-induced turbulence (VIT) is a continuous turbulence source and vehicle exhaust pollutants is a uniform pollution source, the conditions of the hypothesis are preliminarily explored. The research indicates that VIT can be regarded as a continuous turbulence source when vehicles maintain a “safe distance” on the road and form a stable traffic flow. Moreover, according to the range of dispersion of exhaust pollution, a “healthy distance” was proposed to guide driver to avoid direct impact of exhaust emitted from the vehicles in front.