State of the Practice for Determining Motor Vehicle Emission Budget (MVEB) Safety Margins

Focus Area

Air Quality


Air Quality




Under $99k


Under 1 year

Research Idea Scope

Scope: The AASHTO Air Quality Community of Practice May 2012 draft report “Establishing and Coordinating Motor Vehicle Emissions Budgets State-of-the-Practice” recommended an NCHRP study to: “advance the state-of-the-practice for establishing and coordinating MVEBs”. It included the following recommendation:  

“This COP report on developing MVEBs documents the safety margins in NYC, Houston, TX, and Fredericksburg, VA.  A Nationwide NCHRP Research or Synthesis report could expand on this limited data set to … This effort could include additional examples of practices for developing MVEB safety margins, relative and absolute magnitude of the margins, pollutants to which they apply, and the analytical or non-analytical methodology used to determine the margins.  In addition, it could also include a summary of any “lessons learned” or benefits received by the areas utilizing safety margins, and any obstacles to providing such safety margins.”

The draft report includes several related recommendations that could also be addressed in whole or in part in this proposed study. For example, the proposed study could also look at alternative approaches such as emission trading.

Urgency and Payoff

The draft report states in its conclusion that: “…recent changes to several air quality standards and EPA’s emissions model have prompted interest among State DOTs to take a fresh look at how State DOTs, MPOs, and State Air Agencies work together and the processes they use to establish emissions budgets”. Guidance for the establishment of appropriate safety margins that allow for uncertainty in emission forecasts due to changes in models and input data as well as temporary and minor increases in forecasts is needed for transportation agencies to demonstrate conformity in some areas.

Suggested By

Air Quality Community of Practice, AASHTO

[email protected]