Air quality nonattainment areas must use computer models to estimate the mobile source portion of emission inventories for the State Implementation Plan. Mobile source emissions estimates are produced for the emission inventory by multiplying an emission factor by a measured vehicle activity (such as vehicle miles of travel). The Environmental Protection Agency requires the use of their model, MOBILE, to produce emission factors for all states except California. California uses its own emission factor model, EMFAC. Travel demand models, used for transportation planning, produce the needed vehicle activity data. Emissions modeling systems act as an interface between the emission factor models and travel demand models, pulling data from both models to calculate mobile source emissions estimates. This report describes emissions modeling systems that are currently being used or have recently been used for air quality analysis aspects of transportation planning. Both MOBILE and EMFAC are described, and concerns about the accuracy of their emission factors are reported. Each emissions modeling system is described, including major inputs and outputs, and which emission factor model and travel demand model the emissions model will interface with. The authors evaluated each emissions modeling system for possible use in Texas, and found that none of them offer significant advantages in features, accuracy, or ease of use over the emissions modeling system currently being used in Texas.

  • Supplemental Notes:
    • Research study title: Air Pollution Implications of Urban Transportation Investment Decisions.
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  United States  76011

    Texas Department of Transportation

    Research and Technology Transfer Office, P.O. Box 5051
    Austin, TX  United States  78763-5051

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Stephenson, A R
    • Dresser, G B
  • Publication Date: 1994-8


  • English

Media Info

  • Features: References;
  • Pagination: 68 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00672583
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/TX-94/1279-3, Res Rept 1279-3, TTI: 0-1279
  • Contract Numbers: Study No. 0-1279
  • Created Date: Jan 18 1995 12:00AM