Determine Alternative Calculations for Fine Particulate Emission Factors Other Than AP-42 Applicable to Calculate Re-entrained Dust on Transportation Projects

Focus Area

Air Quality


Air Quality




Under $99k


1-2 years

Research Idea Scope

TERI Administrator Note (June 2007): Funded as NCHRP Project 25-25, Task 42

TERI Administrator Note (January 2009): Task reported completed Nov. 2008.

The US EPA emission factor document called “AP-42” provides emission factors for emissions of fine particulate from re-entrained dust on roadways. The way the calculations work, the amount of particulate (dust/silt loading) continues to increase with each passing vehicle. There is no higher limit on the amount of dust that can be created, even when there is only a finite amount of dust available on the roadway. The current tailpipe emission factor model, MOBILE6.2 does not account for re-entrained dust, so the options available to analysts are to either conduct expensive field monitoring to develop site specific emissions or use AP-42 emission factor calculations. The updated MOVES tailpipe emission factor model is also not anticipated to incorporate re-entrained dust emission factors.

The lack of upper limit for dust using AP-42 creates artificially high calculated emissions for transportation projects. To help PM10 and PM2.5 nonattainment and maintenance areas move forward with their transportation projects and provide more accurate data, states need a better tool to use for re-entrained dust calculations.
Identify more accurate, alternative calculation methods (or a more accurate modification of the existing AP-42 method) for fine particulate from re-entrained dust for both paved and unpaved roads that will be acceptable to the US EPA and states.
Task 1:
Conduct a literature search on currently available calculation methods of evaluation for re-entrained dust. Identify all viable field studies on re-entrained dust that used site-specific data. This search should not be limited only to the United States.
Task 2:
Compare the accuracy of calculation methods against known field studies.
Task 3:
Discuss the results of Tasks 1 & 2 with the project chair and steering committee to reach a consensus on scenarios of interest.
Task 4:
Develop draft guidelines on how well the calculations predict the measurements from field studies. Submit to the steering committee.
Task 5:
Make changes in response to committee comments and prepare final guidelines.

Suggested By

Mia Waters, Washington State Dept of Transportation 206/440-4541

[email protected]