Emissions from Diesel-Fueled Heavy-Duty Vehicles in Southern California 2003-01-1901

Few real-world data exist to describe the contribution of diesel vehicles to the emissions inventory, although it is widely acknowledged that diesel vehicles are a significant contributor to oxides of nitrogen (NO_x) and particulate matter (PM) in Southern California. New data were acquired during the Gasoline/Diesel PM Split Study, designed to collect emissions data for source profiling of PM emissions from diesel- and gasoline-powered engines in the South Coast (Los Angeles) Air Basin in 2001. Regulated gases, PM and carbon dioxide (CO₂) were measured from 34 diesel vehicles operating in the Southern California area. Two were transit buses, 16 were trucks over 33,000 lbs. in weight, 8 were 14,001 lbs. to 33,000 lbs. in weight and 8 were under 14,001 lbs. in weight. The vehicles were also grouped by model year for recruiting and data analysis. Emissions were measured in Riverside, CA, using West Virginia University's (WVU) Transportable Medium-Duty and Heavy-Duty Vehicle Emissions Testing Laboratories. The trucks were all exercised through a CSHVR, a Highway cycle, and an Idle period. In addition, selected vehicles were tested under cold start idle, cold start CSHVR, and the Urban Dynamometer Driving Schedule (UDDS). All data were computed in units of g/mile except for idle tests, which were recorded in g/cycle. Repeat runs on the same test schedule demonstrated that data were consistent from run to run. This paper presents the data for the trucks over 33,000 lb. in weight. Data for these trucks showed conclusively that PM levels are higher for older vehicles: this may be due to vehicle age, but more likely is associated with the improved technology for later model years and implied compliance with later standards. In contrast, emissions of oxides of nitrogen (NO_x) have not fallen in the same way with respect to model year. The data provide new insight into real-world diesel truck emissions and will provide information for emissions source profiles for PM source apportionment in Los Angeles. The data reported in this presentation are a portion of the Gasoline/Diesel PM Split Study, sponsored by the U.S. Department of Energy's Office of FreedomCAR and Vehicle Technologies through the National Renewable Energy Laboratory.