An analysis of traffic parameter profiles used in a high resolution mobile source emissions inventory

The purpose of this analysis was to determine the impact of traffic parameter profiles on air pollutant emissions in a high resolution mobile source emissions inventory. The relationship between transportation and air pollution was explained in both qualitative and quantitative terms. The air pollution modeling process was diagramed and explained. The implications for transportation of the Clean Air Act Amendments of 1990 were examined. U.S. EPA guidance concerning the development of traffic parameter profiles for mobile source emissions inventories was provided. Brief explanations of traffic parameter profile development methodologies currently being used were given. The sensitivity of emission factors developed by MOBILE4 to traffic parameter inputs was analyzed. The emission factors for CO, HC, and NOx were found to vary by 80%, 80%, and 20% as speed was increased from 10 mph to 55 mph. NOx emission factors were found to be very sensitive to the HDDV VMT mix fraction. A case study of the development and use of traffic parameter profiles for a mobile source emissions inventory for Tennessee was provided. Emissions produced by two inventory development approaches -- UTK and FTP -- were compared on a countywide and 5 km grid by 5 km grid basis for Rutherford county Tennessee. The emissions developed by the UTK approach were 41% less for CO, 25% less for HC, and 34% higher for NOx on a countywide basis. Grid level emissions of CO for the UTK approach ranged from 12% to 66% less than the FTP approach. The UTK approach produced HC emissions that ranged from 1% to 39% less than the FTP approach when emissions in grids were compared. NOx emissions for the UTK approach ranged from 33% less to 155% more than the FTP approach in individual grids.