ARB Research Seminar

This page updated June 19, 2013

Incidence of Malfunctions, Tampering, and In-Use Emissions for Heavy-Duty Diesel Vehicles

Thomas D. Durbin, Ph.D., College of Engineering Center for Environmental Research and Technology (CE-CERT), University of California, Riverside

September 05, 2007
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Understanding in-use emissions for heavy-duty diesel vehicles (HDDVs) and the factors that contribute to higher in-use emissions, such as malfunctions and tampering, is important for regulatory efforts as well as emissions inventory modeling. In this program, an evaluation of the malfunction and tampering rates in the on-road HDDV fleet was performed and measurements of in-use emissions from HDDVs over the road were made. A number of sources were reviewed to evaluate the incidence of malfunction and tampering. These included existing literature sources, heavy-duty inspection program records, vehicle warranty repair data, non-fleet repair facility records, roadside driver surveys, and electronic diagnostic downloads.

On-road emissions measurements were also made for 5 vehicles ranging in model year from 1996 to 2004. The emissions measurements were made in the Stockton, California area over an on-road course that included highway driving, steady state driving on a surface street, stop and go driving on a surface street, and power lugs. The emissions measurements were made using CE-CERT's Mobile Emissions Laboratory (MEL). The tampering and malfunction rates and in-use emission rates were compared with estimates currently being used in the EMFAC model.

Speaker Biography

Thomas D. Durbin, Ph.D., is an associate research engineer in the emissions and fuels research group of CE-CERT. Dr. Durbin conducts research in a broad range of topics related to vehicle emissions including particulate matter (PM) emissions, diesel, biodiesel, and gasoline fuels, portable emissions measurement systems (PEMS), and the unregulated species such as ammonia, N2O, and toxics. Dr Durbin conducts research in CE-CERT's state-of-of-the-art emissions test facilities including a heavy-duty mobile emissions laboratory, a heavy-duty engine dynamometer laboratory, and a light-duty chassis dynamometer laboratory. Dr. Durbin is also extensively involved with in-field measurements of emissions from passenger cars, heavy-duty trucks, and construction equipment. Prior to joining the emissions and fuel research group, Dr. Durbin was involved in several other areas of research at CE-CERT including renewable energy and fuel sources and advanced vehicle technologies.

Dr. Durbin received his doctorate degree in Physics from the University of California, Riverside, in 1994 where the primary focus of his dissertation was the study of Si films and solid lubricants.

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