ARB Research Seminar

This page updated June 2, 2015

On-Road Measurements of Emissions from Heavy-Duty Diesel Trucks: Impacts of Fleet Turnover and ARB's Drayage Truck Regulation

Photo of Robert A. Harley, Ph.D.

Robert A. Harley, Ph.D., Department of Civil and Environmental Engineering, University of California, Berkeley

June 18, 2015
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


The effects of heavy-duty drayage truck fleet modernization and diesel particle filter (DPF) retrofits were examined through measurements of truck emissions at the Port of Oakland, California. Pollutant concentrations were measured at high time resolution in the exhaust plumes of more than a thousand drayage trucks as they drove toward the Port on a major access road.

Emission factors were matched to data from a statewide drayage truck registry, including engine make, model year, and installed emission control equipment. Between 2009 and 2013, California's Drayage Truck Regulation led to near-universal use of DPFs on Port trucks.

DPF-equipped trucks had substantially lower BC and higher NO₂ emission factors than trucks without DPFs. The newest trucks equipped with both DPFs and selective catalytic reduction (SCR) systems for NOₓ control had the lowest average emission factors for BC and ultrafine particles (UFP), and an average NO₂ emission factor that was about equal to that of the Port truck fleet that was on the road in 2009 before recent emission regulations took effect.

Speaker Biography

Robert A. Harley, Ph.D., is a Professor in the Department of Civil and Environmental Engineering at the University of California, Berkeley, where he has been on the faculty since 1993. Harley's research focuses on air quality and sustainable transportation; he is an author of 95 papers published in peer-reviewed scientific journals, and serves as a co-editor of Atmospheric Chemistry and Physics. He is the inaugural holder of the Carl W. Johnson Endowed Chair in Civil Engineering at Berkeley, awarded in recognition of his record of scholarship and university and professional service. Harley received the National Science Foundation's young investigator (CAREER) award, as well as a visiting scientist fellowship at the University of Colorado/NOAA Aeronomy Lab in Boulder.

Dr. Harley served for three years as Vice Chair of the Civil and Environmental Engineering Department (2001-04), chairing committees responsible for curriculum and student admissions. He also served as Environmental Engineering program leader (2007-10), and Chair of Engineering Science undergraduate programs (2012-15). During 2011, Harley was a visiting scientist at the Max Planck Institute for Chemistry in Mainz, Germany. Harley is also appointed as a Faculty Research Scientist in the Environmental Energy Technologies Division of Lawrence Berkeley National Laboratory, a U.S. Department of Energy science lab located adjacent to campus. Professor Harley holds a bachelor's degree in Engineering Science (Chemical Engineering option) from the University of Toronto, and both M.S. and Ph.D. in Environmental Engineering Science from the California Institute of Technology (Caltech).005).

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