Research Projects

New and upcoming regulations for heavy-duty diesel (HDD) on-road vehicles are expected to provide significant reductions in the emissions from newly purchased HDD vehicles. California also has a Heavy Duty Vehicle Inspection and Periodic Smoke Inspection Program (HDVIP and PSIP) in place for in-use HDD vehicles, but this only monitors smoke opacity. CARB has conducted several pilot studies to understand the incidence of malmaintenance.and tampering in heavy-duty diesel vehicles (HDDVs) and to develop a program to control emissions from in-use trucks. In the earlier Measure 17 or M-17 program, 109 vehicles were tested at the CARB Heavy-Duty Inspection and Maintenance Laboratory (HDIML) facility in Stockton CA over a power lug curve and a steady-state cycle. The objective of the current program was to collect inuse, on-road emissions measurements on a subfleet of 5 vehicles in the Stockton, CA area. Emissions measurements were made with the University of California at Riverside's (UCR's) Mobile Emissions Laboratory (MEL), which is mobile measurement platform with a full dilution tunnel. The results of this study provide information about emissions from in-use HDDVs under typical driving conditions and can be used to better understand emissions inventories and in the development of regulations for in-use vehicles.