An improved CAL3QHC model and the application in vehicle emission mitigation schemes for urban signalized intersections

As an important component of urban roads, signalized intersections have contributed significantly to motor vehicle emissions, which however has not been modelled in high accuracy. This paper uses the International Vehicle Emission (IVE) model to obtain the localized emission factors, so that a dispersion model, CAL3QHC was introduced and modified to incorporate the vehicle acceleration and deceleration states. Two emission reduction schemes for urban signalized intersections, the Green Light Optimal Speed Advisory (GLOSA) system and the no-obstacle driveway design, were proposed, by taking the intersection of Wen'er West Road and Liangmu Road in Hangzhou, China as an empirical example. The overall performance and roadside emission dispersion were simulated using VISSIM software package, with the improved CAL3QHC model. The GLOSA system and the no-obstacle driveway design were found to mitigate the roadside CO concentration by 21.2% and 22.1%, respectively. Findings of the study may assist to monitor roadside pollutant concentrations, formulate and evaluate emission mitigation strategies in urban intersections.