Study On Highway Traffic Emissions For Traffic Operation Management

Traffic operation management measures are increasingly used to improve thetraffic environment now. Control signal optimization and variable speed limit are thecommon traffic operation management measures. This article mainly studied therelationship between speed limits and CO, HC, NOx emission rates under differenttraffic conditions, and the best traffic operation management measures.A test section of S342in Wuxi, China was selected for this study. An integratedmodel was deployed which combined the microscopic traffic simulation modelVISSIM with the emission model established by the data collected from on-boardportable emission measurement system OBEAS-3000. VISSIM recorded thesecond-by-second speed and acceleration of individual vehicle under different speedlimit scenarios as the input data. The emission model output vehicle emissions throughrelating emissions to the instantaneous speed and acceleration of the vehicle. The valueof Speed limit, one-way traffic flow and heavy vehicle percentage is80km/h,1800vphand20%, respectively. Speed limit scenarios were set from50to90km/h at anincrement of5km/h. In order to simulate the different traffic conditions, one-way trafficflow and heavy vehicle percentage scenarios were set from900to3600vph at aincrement of900vph and from0%to30%at a increment of10%, respectively.Distance-based emission rate (mg/km) was used as the performance measure. Thesimulation results showed that, the emission rates of all the three pollutants becamelarger with the increase of traffic flow and heavy vehicle percentage under the samespeed limit value. What’s more, there exists the optimal speed limit value for everypollutant which would result in the least emission rate and the optimal value wouldvary with the changes of traffic flow and heavy vehicle percentage. The variablespeed-limit control is the best traffic operation management measure to get the leastemissions of all the three pollutants.