Quantifying the Contribution of Vehicle Emissions to Local Air Quality
Research Idea Scope
The purpose of this research is to evaluate modeling techniques and ambient measurements to comprehensively understand and explain vehicle emissions contributions to local air quality. The research will consist of three sets of work: 1) a thorough literature review of air quality modeling techniques and available field measurements; 2) a sensitivity-type analysis of modeling techniques and a trend assessment of field measurements for selected case studies identified in the literature review; and 3) modeled-versus-measured comparisons to better understand the application of models necessary to quantify vehicle emissions contributions to local air quality. The research will consider vehicle activity and associated emissions on freeways; at freeway interchanges; on urban arterials; at signalized arterial intersections; at freight terminals; and within transit park and ride lots and parking structures. The research will focus on primary pollutants of concern related to regulatory applications, including criteria pollutants (e.g., carbon monoxide (CO), particulate matter (PM), and nitrogen dioxide (NO2)) and mobile source air toxics (e.g., diesel PM and benzene). The research will examine all relevant emissions models (e.g., MOVES, EMFAC, and AP-42) and dispersion models (e.g., AERMOD, CAL3 series, CALPUFF, R-LINE, and HYROAD). The research will investigate the various emission components linked with vehicle activity, including running exhaust; crankcase running exhaust; start exhaust; crankcase start exhaust; extended idle exhaust; crankcase extended idle exhaust; evap permeation; evap fuel vapor venting; evap fuel leaks; brake wear; tire wear; and re-entrained road dust, as applicable. As part of the literature review, the research will survey readily available databases of field measurements, such as the Federal Highway Administration (FHWA) and Environmental Protection Agency (EPA) near-road studies in Las Vegas and Detroit; EPA’s operational near-road NO2 monitoring sites, which includes measurements of other pollutants and parameters in addition to NO2; and modeling results used by EPA to promulgate the new minimum monitoring requirements for the NO2 monitoring network and accompanying near-road NO2 monitoring technical assistance document. The research will identify any gaps in existing models and any deficiencies in availability of required model inputs, plus possible future research needed to help address any inadequacies. Similar research as to the research proposed here has been completed by the Airport Cooperative Research Program (ACRP) of the Transportation Research Board of the National Academies – ACRP Report 71, “Guidance for Quantifying the Contribution of Airport Emissions to Local Air Quality” sponsored by the Federal Aviation Administration, which may function as a resource.
Urgency and Payoff
Accurate estimation of vehicle emissions and their contribution to overall air quality are essential components in air quality assessments of proposed transportation projects. The combination of ambient air quality measurements and use of modeling tools provides the best available framework to help improve the understanding and measurement of motor vehicle contributions to local air quality. The test case applications of the models combined with field measurements will serve as a guide for completing assessments for similar transportation facilities.
Michael Claggett U.S. Dept. of Transportation, Federal Highway Administration (505) 820-2047