Publication Date


Document Type


Organizational Units

Chemistry and Biochemistry


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


Emission measurements were collected from heavy-duty (HDVs) and medium-duty vehicles (MDVs) at the Peralta weigh station long-term measurement site near Anaheim, CA in 2017. Two Fuel Efficiency Automobile Test units sampled elevated and ground-level exhaust vehicles totaling 2,315 measurements. HDVs (1844 measurements) exhibited historical reductions in fuel specific oxides of nitrogen (NOx) from the 2008 measurements (55%) with increased use of exhaust gas recirculation and selective catalytic reduction systems. However, as these technologies have aged, the in-use benefits have declined. Infrared %opacity measurements of tailpipe soot decreased 14% since 2012 with increased diesel particulate filter (DPF) use, DPF longevity and fleet turnover. 63% of the HDV fleet in 2017 was chassis model year 2011+ compared to only 12% in 2012. The observed MDV fleet (471 measurements) was 1.4 years older than the HDV fleet with average NOx 14% higher. A significant reduction in MDV NOx occurred approximately 2 model years prior to similar HDV reductions (2014 versus 2016 chassis model year). MDV chassis model years 2014+ were able to meet their corresponding NOx laboratory certification standards in-use, whereas HDVs remain slightly above this threshold. Similar MDV NOx emission trends were also observed in data previously collected in Chicago, IL.

Copyright Statement / License for Reuse

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.; Thiruvengadam, A.; Carder, D. K. (2018) Evaluation of Heavy- and Medium-Duty On-Road Vehicle Emissions in California's South Coast Air Basin. Environ. Sci. Technol., 52(22), 13298-13305. DOI: 10.1021/acs.est.8b03994.

Copyright held by the American Chemical Society. User is responsible for all copyright compliance.