The Kansas City Light-Duty Vehicle Emissions Study (KCVES) measured exhaust emissions of regulated and unregulated pollutants from 496 vehicles recruited in the Kansas City metropolitan area in 2004 and 2005. Vehicle emissions testing occurred during the summer and winter, with the vehicles operated at ambient temperatures. One key component of this study was the investigation of the influence of ambient temperature on particulate matter (PM) emissions from gasoline-powered vehicles. A subset of the recruited vehicles were tested in both the summer and winter to further elucidate the effects of temperature on vehicle tailpipe emissions. The study results indicated that PM emissions increased exponentially as temperature decreased. In general, PM emissions doubled for every 20 degrees F drop in ambient temperature, with these increases independent of vehicle model year. The effects of temperature on vehicle emissions was most pronounced during the initial start-up of the vehicle (cold start phase) when the vehicle was still cold, leading to inefficient combustion, inefficient catalyst operation, and the potential for the vehicle to be operating under fuel-rich conditions. The large data set available from this study also allowed for the development of a model to describe temperature effects on PM emission rates due to changing ambient conditions. This study has been used as the foundation to develop PM emissions rates, and to model the impact of ambient temperature on these rates, for gasoline-powered vehicles in the EPA's new regulatory motor vehicle emissions model, MOVES.

Mobile sources significantly contribute to ambient concentrations of airborne particulate matter (PM). Source apportionment studies for PM 10 (PM Յ 10 m in aerodynamic diameter) and PM 2.5 (PM Յ 2.5 m in aerodynamic diameter) indicate that mobile sources can be responsible for over half of the ambient PM measured in an urban area. Recent source apportionment studies attempted to differentiate between contributions from gasoline and diesel motor vehicle combustion. Several source apportionment studies conducted in the United States suggested that gasoline combustion from mobile sources

Ramps serve as the connections between restricted access highways and other road facilities, and considering the intensity of acceleration and deceleration occurring on ramps, the operation on ramps may contribute a significant amount of criteria-pollutant and greenhouse gas emissions from highway operation. In this study, second-by-second speed and position data were collected from 10 vehicles in the Detroit, Michigan, metropolitan area during their daily commute trips in 2012 using a portable activity measurement system. Ramp-associated operations were extracted from these measurements using ArcGIS, and emission rates were assigned based on model runs of the MOtor Vehicle Emission Simulator, or MOVES. In general, emissions of light-duty vehicles estimated for ramp operation are about two to three times higher than those for highway operation (excluding ramps) and local cycles with average speed levels higher than 30 mph. Emissions for interchange ramps are estimated to be similar to highway emissions. Accelerations occurring immediately after vehicles enter the highway from on-ramps contribute a large portion of emissions from ramp operations, since high-power operations are involved. This point applies especially to loop on-ramps, where the emission rate immediately after entering the highways tends to be higher than driving within the physical ramp itself. This research will be useful for understanding basic ramp operation characteristics and their emissions effects, and it will be important for development of ramp classification systems and generic ramp driving cycles, for emissions modeling and ramp hot-spot analysis.