Emission Analysis at Toll Station Area in Beijing with Portable Emission Measurement System

Abstract

The primary objective of this paper is to analyze the emissions around a toll station area in Beijing by using a portable emission measurement system (PEMS). To this end, the real-world vehicle emission and activity data of a light-duty-gasoline vehicle, a 2000 Volkswagen Jetta, were collected at a freeway toll station in Beijing with the PEMS. The data on both electronic toll collection (ETC) lanes and manual toll collection (MTC) lanes were assembled for comparison. Then an analysis showed that all emissions were reduced by using ETC; however, the reduction in nitrogen oxide (NOx) emission was much less than that for hydrocarbons (HC) and carbon monoxide (CO) for the testing vehicle. Further, emission estimation approaches based on vehicle specific power (VSP) were studied with the collected data, and some errors in common were identified. For the toll station, the VSP interval [-2, 2] was found to be a critical interval in the driving modes as well as in the average emission rates. A finer binning approach was applied, and the accuracy of the emission estimation for the toll station was improved. Subsequently, a comprehensive analysis of speed, VSP, and the accumulated emissions around the tollbooths was conducted to explain why the percentage of NOx reduction was much less than those for HC and CO. Finally, a queue-based emission estimation model was studied for the MTC lanes by using the field data, and the model was found not suitable for the estimation of NOx emission.