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Document Type


Organizational Units

Chemistry and Biochemistry


Atmospheric chemistry, Emissions, Pollutants, Heavy-duty diesel trucks


Two California heavy-duty fleets have been measured in 2013, 2015 and 2017 using the On-road Heavy-duty Measurement System. The Port of Los Angeles drayage fleet has increased in age by 3.3 model years (4.2 to 7.5 years old) since 2013, with little fleet turnover. Large increases in fuel specific particle emissions (PM) observed in 2015 were reversed in 2017, returning to near 2013 levels, suggesting repairs and or removal of high emitting vehicles. Fuel specific oxides of nitrogen (NOx) emissions of this fleet have increased and NOx after-treatment systems do not appear to perform ideally in this setting. At Cottonwood weigh station in northern California, the fleet age has declined (7.8 to 6 years old) since 2013 due to fleet turnover significantly lowering the average fuel specific emissions for PM (-87%), black carbon (-76%) and particle number (-64%). Installations of retrofit-diesel particulate filters in 2007 and older vehicles have further decreased particle emissions. Cottonwood fleet fuel specific NOx emissions have decreased slightly (-8%) during this period, however, newer technology vehicles with selective catalytic reduction systems (SCR) promise an additional factor of 4 to 5 further reductions in the long-haul fleet emissions as California transitions to an all SCR equipped fleet.

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Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Publication Statement

This is an Accepted Manuscript for

Haugen, M. J.; Bishop, G. A. (2018) Long-Term Fuel-Specific NOx and Particle Emission Trends for In-Use Heavy-Duty Vehicles in California. Environ. Sci. Technol., 52(10), 6070-6076. DOI: 10.1021/acs.est.8b00621.

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Molly J. Haugen, Gary A. Bishop


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English (eng)


32 pgs

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590 KB