Environmental Services and Planning

Air Quality Planning

Motor Vehicle Emissions Budgets (MVEB)

Transportation conformity requires transportation plans, programs and projects in any nonattainment area for carbon monoxide, nitrogen dioxide, particulate matter, or ozone to evaluate air quality impacts before receiving Federal approval. The Arizona Department of Environmental Quality (ADEQ) submits air quality plans to the Environmental Protection Agency (EPA) that contains an emissions inventory of all sources that emit pollutants into the air. These air quality State Implementation Plans (SIPs) contain a cap on vehicle emissions, this limit on emissions is referred to as a Motor Vehicle Emissions Budget (MVEB). The EPA determines whether any MVEB established in an SIP is adequate for transportation conformity purposes, a list of approved budgets can be found on EPA's website.

The EPA also approves the type of emissions models that can be used to estimate transportation related emissions for a "regional conformity analysis" and project level "hot spot" analysis. MPD Air Quality uses these models for regional conformity analysis when necessary and also provides local agencies with specific motor vehicle registration data required to run these models, for more information contact MPDAirQuality@azdot.gov.

Recent EPA Guidance on emissions models used for transportation:

  • For tailpipe emissions: MOtor Vehicle Emission Simulator model (currently MOVES2010a) is required for regional emissions analyses for transportation conformity determinations “regional conformity analyses” starting March 2, 2013. The EPA is also requiring the use of MOVES2010a for Project level “hot spot” analysis starting Dec. 20, 2012.
  • For re-entrained road dust: The EPA uses "AP-42: Compilation of Air Pollutant Emission Factors" to estimate road dust from paved and unpaved roadways. AP-42 Methods for Estimating Re-Entrained Road Dust from Paved roads 13.2.1 was updated on January 2011 and required for regional conformity analysis Feb. 4, 2013. The current AP-42 Methods for Unpaved Roads can be found in section 13.2.2 last updated November 2006.