Assessment of Regulatory Air Pollution Dispersion Models to Quantify the Impacts of Transportation Sector Emissions

State departments of transportation (DOTs) conduct project-level air quality analyses to conform to the National Environmental Policy Act (NEPA) and meet transportation conformity rule requirements where applicable. DOTs are interested in a rigorous and systematic model review and update process for regulatory dispersion models for the transportation sector to ensure that the models generate credible results. In this context, the Airport Cooperative Research Program (ACRP) Report 71, Guidance for Quantifying the Contribution of Airport Emissions to Local Air Quality, provides information on modeling assessments and is a helpful reference. Another key reference is the 2007 National Research Council (NRC) report, Models in Environmental Regulatory Decision-Making, which called for consideration of multiple criteria for model assessments. Building on ACRP Report 71, the 2007 NRC report, Models in Environmental Regulatory Decision-Making, and other studies, DOTs would benefit from additional research that comprehensively examines project-level air quality dispersion models and assesses their respective strengths and weaknesses. The objective of this research is to produce a technical report for decision makers to identify the appropriate air quality dispersion models for regulatory applications in the transportation sector. The technical report should: (1) specify procedures to test air quality dispersion models using real-world air quality data (which must include data from tracer studies) for regulatory applications in the transportation sector for criteria pollutants typically assessed in project level analysis; (2) apply these procedures to conduct detailed evaluation of selected models against air quality field data; (3) based on the results of the analyses, evaluate the strengths and weaknesses of dispersion models for specific transportation regulatory applications for each pollutant; (4) present comparative analyses (including technical and methodological evaluations) to provide insights into why a particular model is the best performing model for those specific transportation applications; and (5) make recommendations for model improvements based on the model assessments and comparative analyses. The technical report should address a broad range of components related to the project objective such as, but not limited to, the following: (1) Identification of the key elements of a preferred model review and update process or model improvement program (MIP) for regulatory dispersion models for the transportation sector, considering the concepts presented in the 2007 NRC report, Models in Environmental Regulatory Decision Making; (2) Data collection for model evaluation, including data from existing tracer studies, and, if needed, additional field studies; (3) Comprehensive model evaluation against real-world data for regulatory analysis including assessments (with statistical analyses) of alternatives for compliance with the National Ambient Air Quality Standards (NAAQS) and build/no-build scenarios. Uncertainty in background concentrations must be addressed. Examples of regulatory applications include facility types (e.g., highway segments and interchanges, intersections, truck and bus terminals); configurations (e.g., skewed or un-skewed intersections and interchanges); operating conditions (e.g., congested vs uncongested); and setting (urban versus rural); and (4) Model assessment processes that include periodic reviews and extensive consultation with stakeholders (including DOTs, who will have full access to all data, models, and other relevant information considered in the reviews); assessment against standard technical criteria (accuracy/uncertainty, efficiency and proportionality); comparative analyses; and overall determination of the adequacy of each of the models for their intended regulatory application for transportation projects for each pollutant.


  • English


  • Status: Proposed
  • Funding: $700000
  • Contract Numbers:

    Project 25-55

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Rogers, William

  • Start Date: 20180419
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 41651

Subject/Index Terms

Filing Info

  • Accession Number: 01634965
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 25-55
  • Files: TRB, RiP
  • Created Date: May 19 2017 1:00AM