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Transportation Conformity Highlights

October 2005

FHWA Posts 8-Hour Ozone and PM2.5 Maps on Website. FHWA has recently posted maps of each 8-hour ozone and PM2.5 nonattainment area on its website. The maps were developed to show the boundaries of the designated 8-hour ozone and PM2.5 nonattainment areas and how they relate to the boundaries of associated 1-hour ozone nonattainment areas, as well as any associated MPOs. To view the maps, go to: and

MOBILE6.2 Modeling for Use of Reformulated Gasoline (RFG) in Winter. If you are modeling winter reformulated gasoline (RFG) using MOBILE 6.2, please be aware that you will need to provide user-specified values in order to get the correct results. The MOBILE6.2 User's Guide instructs modelers to use the EVALUATION MONTH and SEASON commands to specify winter RFG. However, this option is not functioning as designed; MOBILE6.2 continues to use summer RFG values in spite of these inputs. As a result, modeling for winter months will actually incorporate summer gasoline sulfur values in RFG areas, which will cause the model to underestimate VOC, NOx and PM2.5 emissions. This is primarily an issue for the 2002 calendar year, and appears to affect only RFG areas. Underestimating 2002 emissions could result in difficulties passing a build-no-greater-than-2002 test for conformity, and may result in errors in developing SIP emission inventories and emissions budgets.

EPA's recommendation for addressing this problem is to enter wintertime RFG parameters manually in MOBILE6.2, using the FUEL PROGRAM/4 (user-specified sulfur levels), OXYGENATED FUELS, and FUEL RVP commands. This error does not affect model calculations involving diesel sulfur content. For more information, contact Jeff Houk, FHWA Resource Center (

PM2.5 Transportation Conformity Workshops. During August and September of 2005, the Transportation Conformity Team of the Office of Natural and Human Environment, in cooperation with EPA's Office of Transportation and Air Quality (OTAQ), conducted several transportation conformity training sessions. These workshops focused on implementing conformity requirements in PM2.5 nonattainment areas as well as included preliminary discussions of SAFETEA-LU conformity changes. EPA sponsored three workshops in Chicago, IL; Charleston, SC; and Newark, NJ. FHWA conducted 5 additional workshops in Indianapolis, IN; Sacramento, CA; Columbus, OH; Frankfort, KY; and St. Louis, MO. Over 250 conformity practitioners from FHWA and FTA field offices, EPA regional offices, State DOTs, State air agencies, MPOs, and consultants attended these workshops. For more information, contact Gary Jensen or Emily Tait.

Multiple Source Air Toxics (MSAT) Workshops Scheduled. The FHWA Resource Center is presenting two MSAT workshops this Fall. The workshops cover the emerging issue of project-level MSAT analysis in NEPA documents. The two-day workshops include background on MSATs, overview of quantitative and qualitative analysis techniques, examples of recent project-level analysis methodologies, and uncertainties involved in MSAT assessments. Also included are technical issues, defining an MSAT study area, MBOILE6.2 MSAT modeling, and other sources of emissions that can be considered in MSAT analysis. A hands-on workshop involving use of MOBILE6.2 for a hypothetical MSAT analysis is offered on the second day. The workshops will be held in Seattle, WA on October 24-25 and Minneapolis, MN on November 9-10. For information on the Seattle workshop contact Mia Waters at WSDOT, 206-440-4541. For information on the Minneapolis workshop, contact Peter Wasko, MNDOT at 651-582-1293.

NTI Course: Introduction to Transportation Conformity. Courses will be offered in Los Angeles, CA on October 26-28; Charleston, WVA on November 1-3; Dover, DE on December 6-8; and Chattanooga, TN on January 17-19, 2006. For information and to register go to:

Estimating Regional Mobile Source Emissions Course Scheduled. The NHI course on Estimating Regional Mobile Source Emissions will be held in Arlington, VA from November 15-19, 2005. For more information and to register see: (link disabled).

FHWA Resource Center Training Activities.FHWA's Resource Center Air Quality Technical Services Team is available to offer air quality-related training opportunities and information can be found at:

If you have any suggestions for future monthly conformity highlights, please email:

FHWA Resource Center Air Quality Team Contacts:

Updated: 1/31/2017
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