The main objective of this paper is to evaluate the emissions implications of old U.S. vehicles that are imported to Mexico. The paper presents a field emissions data collection of a sample of five light-duty gasoline vehicles that are registered in Juarez, Mexico and frequently cross into El Paso, Texas. The gaseous (carbon dioxide [CO2], carbon monoxide [CO], nitrogen oxides [NOx], and total hydrocarbons [THC]) and particulate matter (PM) emissions rates were measured using two portable emissions measurement systems (PEMS). The collected emissions data were analyzed according to operating modal bin concept that is implemented in EPA's MOVES model. The second-by-second emissions rates were grouped into operating mode bins based on their corresponding Vehicle Specific Power (VSP) and speed values. Modal average emission rates were then estimated for each bin using all the observations that fall into that modal bin. It is found that the operating mode bins provides satisfactory estimate for low-grade and uphill driving conditions. Care must be taken when these rates are used for estimating emissions of low-load conditions such as downhill traffic on high-grade roads. A cycle-based analysis was performed using the drive cycles implemented in MOBILE6.2 model. The results show that two of the tested vehicles emitted higher amounts of CO, NOx, THC, and PM emissions than the others and MOBILE6.2 rates. CO2 emissions of all the tested vehicles were found to be at approximately the same level as estimated by MOBILE6.2. The results of this study will be used to evaluate the cost-effectiveness of using programs aimed at improving air quality at U.S.-Mexico border region.
Abstract