Atmos. Chem. Phys. Discuss., 12, 18715-18740, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Cost effective determination of vehicle emission factors using on-road measurements
N. Hudda1, S. Fruin1, R. J. Delfino2, and C. Sioutas3
1Department of Preventive Medicine, Environmental Health Sciences, University of Southern California, Los Angeles CA 90089, USA
2Department of Epidemiology, School of Medicine, University of California, Irvine, CA 92617, USA
3Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA

Abstract. To evaluate the success of vehicle emissions regulations, trends in both fleet-wide average emissions as well as high-emitter emissions are needed, but it is challenging to capture the full spread of vehicle emission factors (EFs) with chassis dynamometer, tunnel or remote sensing studies. We developed an efficient and cost-effective method using real-time on-road pollutant measurements from a mobile platform, which when linked with real-time traffic data, allows calculating both the average and spread of EFs for light-duty gasoline-powered vehicles (LDV) and heavy-duty diesel-powered vehicles (HDV). This is the first study in California to report EFs under a wide range of real-driving conditions on multiple freeways and it captured much or most of the variability in EFs due to inter-vehicle differences. Fleet average LDV EFs were generally in agreement with most recent studies and an order of magnitude lower than HDV EFs, but over an order of magnitude or more spread was observed for both LDV and HDV EFs. HDV EFs reflected relatively rapid decreases occurring in diesel emissions in Los Angeles/California, and HDV EFs on I-710, a primary route used for goods movement and a focus of additional truck fleet turnover incentives, were lower than on other freeways. When freeway emission rates (ER) were quantified as the product of EF and vehicle activity rates per mile of freeway, ERs were found to be generally similar in magnitude. Despite a two- to three-fold difference in HDV fractions between freeways, higher LDV volumes largely offset this difference.

Citation: Hudda, N., Fruin, S., Delfino, R. J., and Sioutas, C.: Cost effective determination of vehicle emission factors using on-road measurements, Atmos. Chem. Phys. Discuss., 12, 18715-18740, doi:10.5194/acpd-12-18715-2012, 2012.
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