Effects of Heavy-Duty Diesel Vehicle Idling Emissions on Ambient Air Quality at a Truck Travel Center and Air Quality Benefits Associated with Advanced Truck Stop Electrification Technology

United States Department of Transportation (DOT) requires truck drivers to rest for 10 hours after every 14 hours of driving. During this time and while waiting for loading and unloading of their trucks, truck drivers idle their engine to provide heat or air conditioning for the cab and sleeping compartment, keep the engine warm during cold climate, and provide electrical power for their onboard appliances. At large truck stops, 200 or more trucks may be idling at the same time. At these truck stops idling emissions can significantly contribute to the concentrations of NOx and PM_2.5 pollutants in the ambient air in the vicinity of the truck stop.

In this study monitoring of ambient air at the Petro truck travel center located at I40/I75 and Watt Road interchange was performed between mid December 2003 and August 2004. Concentrations of PM_2.5 and NOx were measured continuously at two locations. Computer modeling was also performed using EPA’s ISCST3 model to predict ambient concentrations of PM_2.5 and NOx at the truck stop. Ambient concentrations of NOx and PM_2.5 were found to be higher at nighttime and early morning hours compared to daytime. The number of trucks idling at the truck travel center was also found to have similar trend as that of ambient concentrations of considered pollutants. Average ambient concentrations of 276 ppb and 213 ppb of NOx and 35 mg/m³ and 29 mg/m³ of PM_2.5 were monitored at the two selected locations over the course of this research. The monitored concentrations of PM_2.5, and NOx were then compared to the predicted values in an effort to verify and calibrate the model. The ISCST3 model was used to predict annual average and maximum 24-hour average NOx and PM_2.5 and concentrations in the Watt Road area and three hot-spots corresponding to the three truck travel centers at the area were observed. If sufficient number of IdleAire electrification units were provided to accommodate all trucks (that would otherwise idle), the ambient concentrations (not considering background concentrations) would be lower by 70% and 48% at the two monitoring locations as predicted by ISCST3 model.