Influences of Crest Vertical Curve Curvature on Exhaust Emissions of Heavy-Duty Diesel Trucks at Grade Change Point Section in Highway

Abstract

The vertical curve is a major factor affecting vehicle exhaust (CO2, CO, NOx, PM2.5) emissions. This article takes a heavy-duty diesel truck as a typical vehicle, combining instantaneous speed, acceleration and the vehicle-specific power VSP to divide the operating mode, and the exhaust emission of a heavy-duty diesel truck is then calculated by using MOVES. Finally, the environmental modification factors (EMFs) are used to evaluate the influence of curvature change on the exhaust emissions. The results show that CO2 and PM2.5 emissions of heavy-duty diesel trucks are increasing with the curvature of the crest vertical curve changing; with the increase and decrease of curvature K of the crest vertical curve by 50%, CO and NOx emissions showed an increasing trend. Among the four main emissions, CO2 emission amount is the largest, followed by NOx, CO and PM2.5. The emission rates of CO2 and PM2.5 increase with the increase of curvature of the crest vertical curve, and the minimum values of CO2 and PM2.5 emission rates are 46.7 g/s and 0.022 g/s, respectively. The emission rates of CO and NOx increase with the increase of curvature. The minimum point of emission rates of CO and NOx are 0.042 g/s and 0.259 g/s, respectively.