CARB Research Seminar

This page updated March 2, 2018

Investigate the Durability of Diesel Engine Emissions Controls

Photo of Gary A. Bishop, Ph.D.

Gary A. Bishop, Ph.D., University of Denver

March 30, 2018
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Recent tightening of heavy-duty diesel engine emission standards, as well as in-use regulations such as the Truck and Bus Rule, have spurred the widespread adoption of diesel particulate filters (DPFs) and selective catalytic reduction (SCR) by California’s on-road heavy-duty fleet. Real-world observations of both PM (removed by DPFs) and NOX (removed by SCR) emitted from individual heavy-duty trucks are required to determine how successful these regulatory efforts have been. Gary Bishop and colleagues at the University of Denver have measured emissions of these and other pollutants from trucks leaving the Port of Los Angeles and at the Cottonwood weigh station using a custom On-road Heavy-duty Measurement System (OHMS). OHMS was deployed three times at each site, in 2013, 2015, and 2017. They made an average of approximately 1200 measurements in each of these six campaigns. The Port fleet, a fully DPF equipped fleet by 2012, has steadily aged and shown that most real-world DPFs perform well, but some can fail leading to high PM emissions. NOX emissions have slowly increased (21 to 27 g NOX/kg of fuel) and lower operating temperatures are likely the reason that newer SCR equipped Port vehicles (2011 & newer) fail to show the promised emission benefits. The Cottonwood fleet has experienced a steady fleet turnover and with the newer fleet (-1.7 yrs.) both particulate (0.22 to 0.08 gPM/kg of fuel) and NOX emissions (20.3 to 16 g NOX/kg of fuel) have declined. Newer SCR equipped vehicles gives the promise of an additional factor of 3 reduction in fuel specific NOX emissions by 2023.

Speaker Biography

Dr. Gary A. Bishop is a research scientist in the Department of Chemistry and Biochemistry at the University of Denver. He obtained his Ph.D. degree in bio-physical chemistry from the University of Colorado at Boulder in 1986. Since then, Dr. Bishop has developed and deployed instruments that measure real-world vehicle emissions. This instrumentation has been used to characterize light-duty vehicle fleets in more than 21 countries and in more than 30 US locations. It has also been used to measure emissions from heavy-duty diesel trucks in both the United States and Switzerland, commercial aircraft in London, snowmobiles in Yellowstone National Park and line-haul locomotives in Nebraska. His work has resulted in coauthoring 10 patents and more than 50 peer reviewed journal publications.

For a complete listing of the ARB Research Seminars and the related documentation
for the seminars please view the Main Seminars web page