ARB Research Seminar

This page updated May 10, 2017

Activity Patterns of Heavy-Duty Vehicles and Their Implications on Real-World In-Use Emissions

Photo of Kanok Boriboonsomsin, Ph.D.

Kanok Boriboonsomsin, Ph.D., P.E., Associate Research Engineer, Center for Environmental Research and Technology, University of California, Riverside.

May 31, 2017
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Heavy-duty vehicles comprise a variety of vocations, each of which may have different operational requirements resulting in different vehicle and engine activity patterns. It is important to understand the extent of these differences so that appropriate emission control strategies and policies can be developed. For instance, many heavy-duty diesel vehicles employ the selective catalytic reduction (SCR) technology to meet the 2010 emission standards for nitrogen oxides (NOₓ). Typically, SCR needs to be at least 200 C before significant NOₓ reduction is achieved. Some activity patterns may increase the likelihood that this SCR temperature requirement is not met, such as during start-up and idling. The frequency of the activity patterns contributing to low SCR temperature varies partly by the vehicle's vocational use.

In this study, the researchers collected detailed vehicle and engine activity data from 90 California heavy-duty vehicles across several vocations including line haul, drayage, construction, food and beverage distribution, refuse, and utility repair, among others. The data were used to calculate a number of statistics related to trip, engine start, engine idle, SCR temperature, etc. This presentation will highlight some of the similarities and differences in these statistics among heavy-duty vehicles in different vocations. For example, it is found that the vehicles in this study operate with SCR temperature lower than 200 C for 11-87% of the time, depending on their vocation type. As a result, the estimated reduction in engine-out NOₓ emission by SCR ranges from 16% for agricultural trucks to 69% for refuse trucks. This would have a significant impact on the real-world in-use NOₓ emission inventory of heavy-duty diesel vehicles in California.

Speaker Biography

Kanok Boriboonsomsin, Ph.D., P.E., is an Associate Research Engineer in the College of Engineering - Center for Environmental Research and Technology (CE-CERT), University of California, Riverside. His research focuses on sustainable transportation, vehicle activity analysis, vehicle energy and emissions modeling, intelligent transportation system, as well as connected and automated vehicle technology. Dr. Boriboonsomsin is a key member of CE-CERT's Sustainable Freight Research Initiative. Dr. Boriboonsomsin was recently appointed the Vice Chair of the Vehicle Technology and Activity Subcommittee of the Transportation Research Board's Transportation and Air Quality Standing Committee.

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