气候变化领域集成服务门户

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.