Publication Date


Document Type


Organizational Units

Chemistry and Biochemistry


Atmospheric chemistry, Emissions, Pollutants


The global economic recession of 2008 - 2010 severely depressed light-duty vehicle sales in the United States. On-road fleets observed with a remote vehicle exhaust sensor in 2013 at three historical sampling locations in Denver, Los Angeles and Tulsa showed large reductions in the fleet fractions of 2009 model year vehicles of 40%, 38% and 35% respectively when compared to prerecession 2007 levels with the light-duty truck category suffering the largest percentage declines. The fleet fraction for these ~5 year old vehicles is normally reserved for vehicles more than twice their age. This resulted in a significant increase in the on-road freeway fleet age, which had been relatively stable. The fleet average age increased by two years in Denver and Los Angeles but only by one year in Tulsa, likely due to its faster economic recovery. Using fleet fractions from previous data sets we estimated age adjusted mean emissions increases for the 2013 fleet to be 17 to 29% higher for carbon monoxide, 9 to 14% higher for hydrocarbons, 27 to 30% higher for nitric oxide and 7 to 16% higher for ammonia emissions than if historical fleet turnover rates had prevailed.

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

Bishop, G. A.; Stedman, D. H. (2014), The Recession of 2008 and its Impact on Light-duty Vehicle Emissions in Three Western US Cities, Environ. Sci. Technol. 48, 14822-14827. DOI: 10.1021/es5043518.

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

Rights Holder

Gary A. Bishop, Donald H. Stedman


Received from author

File Format



English (eng)


25 pgs

File Size

444 KB