A Methodology for Evaluating Mobile Source Air Toxic Emissions Among Transportation Project Alternatives

With the final update to its on-road mobile source emission factor model, MOBILE6.2, the U.S. Environmental Protection Agency (EPA) added capabilities of predicting emission factors for a select number of mobile source air toxics (MSAT), commonly referred to as the six priority MSATs. These are acetaldehyde, acrolein, benzene, 1,3-butadiene, diesel particulate matter, and formaldehyde. This presentation describes a methodology for computing and evaluating emissions of MSATs among a group of transportation project alternatives. The suggested scale of analysis is the affected transportation network, defined as those links where the annual average daily traffic is expected to change by ± 5% or more as a result of the project. This analysis scale is considered reasonably representative of the regional scale emission factors predicted by MOBILE6.2. To gauge how emissions could change over an affected transportation network, provided are calculation ranges of MSAT emission factors produced by the model due to changes in a variety of input parameters. These include calendar year, ambient temperature, fuel Reid vapor pressure, and vehicle speed. Finally, a technique is presented for assessing MSAT emissions from the affected transportation network considering their relative toxicities. The technique allows a way to gauge the importance of increases and decreases in individual MSAT species amid proposed transportation alternatives and/or mitigation measures.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 21p

Subject/Index Terms

Filing Info

  • Accession Number: 01609448
  • Record Type: Publication
  • Created Date: Aug 22 2016 2:48PM