Effects of the abolishment of London western charging zone on traffic flow and vehicle emissions

Abstract

This paper applies the regression discontinuity method to evaluate the effects of the removal of London western charging zone (WCZ) scheme on the traffic flow characteristics and traffic-related emissions, based on the data of 525 road sections. First of all, continuity of the confounders is assessed. Results indicate that all the confounders are continuous at the cutoff. Then, the impacts of implementing and abolishing the WCZ scheme are investigated. Results indicate that the overall traffic volume is reduced by 31% after implementing the WCZ scheme. On the contrary, the overall traffic volume in the concerned area is increased by 26% after the abolishment. For the environmental effects, results indicate that the traffic-related NOX and CO2 emissions are reduced by 29% and 33% respectively after implementing the WCZ scheme and bounced back by 24% and 21% respectively after the abolishment. These imply that there are moderate residual effects for the removal of WCZ scheme on the traffic volume and traffic-related CO2 emission. However, the residual effect on the traffic-related NOx emission is marginal.