ARB Research Seminar

This page updated March 6, 2019

Heavy-Duty On-Road Vehicle Inspection and Maintenance Program

Photo of Thomas D. Durbin, Ph.D.

Thomas D. Durbin, Ph.D., University of California, Riverside

March 27, 2019
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


On-road heavy-duty (HD) vehicles represent one of the most important sources of emissions in California. Emissions from on-road heavy-duty vehicles are major contributors to poor air quality in California. Although existing regulations have provided significant reduction in terms of control of both nitrogen oxides (NOx) and particulate matter (PM) emissions with exhaust aftertreatment, HD vehicles still represent 33% of NOx emissions, 26% of PM emissions, and 8% of greenhouse gas (GHG) emissions from motor vehicles based on EMFAC2014 estimates. California's current roadside heavy-duty vehicle inspection program includes opacity testing, and checks for emission control labels and tampering. The fleet inspection program requires California-based fleets with two or more heavy-duty vehicles to conduct annual opacity testing. Neither program includes inspections for NOx emissions control from the in-use fleet, nor have they kept pace with advances in diesel engine technology, such as aftertreatment for PM and NOx control and the use of on-board diagnostics (OBD). In order to better ensure that modern diesel engines are maintained and repaired to continue to meet emissions performance requirements in-use, California is now in need of a more comprehensive HD I/M program.

The objective of this study is to evaluate and assess possible options for a more comprehensive HD I/M program that could be implemented in California. For this study, a pilot study with nominally 50 vehicles was conducted at a local repair facility. The pilot study included an evaluation of pre- and post-repair emissions reductions and the repair costs. A suite of different instruments potentially applicable to a HD I/M program were also evaluated, including mini-PEMS and the Emissions Detecting and Reporting (EDAR) remote sensing device. This information is being used in a broader analysis of the cost-effectiveness and emission benefit impacts of the implementation of such an enhanced I/M program statewide. The study results could be used by the CARB to help inform staff as it develops a comprehensive HD I/M program as part of its broader policy umbrella to meet federally-mandated ambient air quality standards and CARB's overall air quality, sustainable freight, and climate goals.

Speaker Biography

Dr. Durbin is a Research Engineer in the emissions from advanced vehicles and fuels research group of CE-CERT and an adjunct professor in the Chemical and Environmental Engineering Department. He is conducting research in the area of vehicle emissions with an emphasis on studying particle and in-use emissions, fuels, and advanced technology vehicles. Prior to joining the vehicle emissions group, Dr. Durbin was involved in several other areas of research at CE-CERT including renewable energy and fuel sources and advanced vehicle technologies. Tom Durbin received his doctorate degree in Physics from the University of California, Riverside, in 1994.

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