Regulated Emissions from Heavy Heavy-Duty Diesel Trucks Operating in the South Coast Air Basin

Heavy duty diesel vehicle (HDDV) emissions are known to affect air quality, but few studies have quantified the real-world contribution to the inventory. The objective of this study was to provide data that may enable ambient emissions investigators to m,odel the air quality more accurately. The 25 vehicles reported in this paper are from the first phase of a program to determine representative regulated emissions from Heavy Heavy-Duty Diesel Trucks (HHDDT) operating in Southern California. Emissions data were gathered using a chassis dynamometer, full flow dilution tunnel, and research grade analyzers. The subject program employed two truck test weights and four new test modes (one was idle operation), in addition to the Urban Dynamometer Driving Schedule (UDDS), and the AC50/80 cycle. The reason for such a broad test cycle scope was to determine thoroughly how HHDDT emissions are influenced by operating cycle to improve accuracy of models. Overall, it was determined from these Phase 1 data that oxides of nitrogen (NO_x) emissions did not decrease in relation to the HHDDT Model Year (MY) and all MY bins produced about 20 g/mile of NO_x on the UDDS. However, particulate matter (PM) emissions decreased in relation to MY and hydrocarbon (HC) and carbon monoxide (CO) emissions showed a slight decrease in relation to MY for some of the test schedules. For idle operation, NO_x emissions were lowest for the pre-1990 MY group of HHDDT. After reading results of this study, readers are likely to appreciate the challenges that have been faced by air quality investigators as they attempt to incorporate emissions inventory data into ambient models.