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Transportation Conformity Highlights

April 2006

Transportation Conformity Guidance for Hot-Spot Analysis in PM10 and PM2.5 Nonattainment and Maintenance Areas. EPA and FHWA recently released this guidance which is a companion document to the March 10, 2006, final rule that establishes the transportation conformity criteria and procedures for determining which transportation projects must be analyzed for local air quality impacts in PM2.5 and PM10 nonattainment and maintenance areas (71 FR 12468). The EPA and FHWA have developed this guidance to help state and local agencies meet the final rule's hot-spot analysis requirements. The guidance can be found at:

FHWA Updates Transportation Conformity Reference Guide. The Transportation Conformity Reference Guide has been updated and is now available. The Guide has been updated to reflect the July 1, 2004 and May 6, 2005 conformity rule changes and the statutory changes made to the transportation planning and conformity processes as a result of enactment of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU). The Reference Guide can be found at:

EPA Updates Particulate Matter Emission Rates for MOBILE6.2. EPA identified an error in MOBILE6.2 that causes it to underestimate the benefits of the 2007 heavy-duty diesel standards, and is publishing a fix on its website. The default emission rates provided with MOBILE6.2 do not completely account for the effects of the recent remissions standards that affect PM emissions for 2007 and newer model year heavy-duty diesel vehicles. As a result of this error, PM emission rates for 2007 and newer model year heavy duty vehicles are slightly higher than intended and do not reflect the complete benefits of the emission standards described in EPA's 2007 Heavy-Duty Highway Final Rule. MOIBLE6.2 users should stop using the external data files related to PM emissions originally distributed with the MOBILE6 model. The updated data file including background information can be found at:

FHWA Resource Center to Hold PM2.5 Hot-Spot Webcast. The FHWA Resource Center will be offering a webcast on PM2.5 Hot-Spot qualitative guidance. The date has not yet been set. The workshop is specifically designed for project sponsors and FHWA Division staff that will need to know how to conduct PM2.5 qualitative guidance. For more information see:

REMINDER: End of Grace Period is Approaching for Required use of MOBILE6.2 and AP-42 for PM10 conformity analysis. EPA's 2-year grace period, which ends on May 19, 2006, requires that, in most cases, MOBILE6.2 and AP-42 be used in new PM10 conformity analyses. For more information, see EPA's guidance on use of MOBILE6.2 and AP-42 at:

REMINDER: HPMS reassessment to look at changing business needs. In light of the recent authorization of SAFETEA-LU and the changing business needs of both our internal and external customers, the FHWA Office of Highway Policy Information is conducting a periodic reassessment of the Highway Performance Monitoring System. The HPMS' purpose has always been to provide data that reflects the extent, condition, performance, use, and operating characteristics of the Nation's highways. It is also the data used to calculate the vehicles miles of travel (VMT), a key data item when used in establishing regional transportation-related emissions for transportation conformity purposes.

To identify the changing needs for accurate, appropriate, and timely data related to meet HPMS' purpose, the FHWA is conducting a reassessment process to determine what improvements may be necessary to maintain and enhance this national highway database.

A series of regional outreach meetings will be held to seek input and generate discussion of what direction HPMS should take by the year 2010. Findings will be documented and recommendations will be formulated on behalf of these meetings and other public comment. These meetings are to be held in Washington, DC (April 10-11, 2006), Hartford, CT (April 26-27, 2006), Atlanta, GA (May 10-11, 2006), Portland, OR (May 24-25, 2006), and Lincoln, NE (May 31-June 1, 2006). The entire reassessment is expected to take 18 months. All interested, including State Highway Agencies, MPO's, regional councils, consultants, academia, and others that make use of highway data are encouraged to take part. For more information, please contact Ralph Volpe at 202-366-4048 or visit the website at

FHWA Updates Transportation and Air Quality Fact Book. FHWA recently released the 2006 Transportation Air Quality Facts and Figures Book. The document is full of good information on air pollutants, travel trends, emission trends, greenhouse gas emissions, air toxics, emission standards and other transportation-related facts and figures. Copies of the publication can be obtained by contacting: Victoria Martinez at (787) 766-5600 ext. 231 or

EPA Releases Diesel Retrofit Technology Report. EPA recently released a report entitled "Diesel Retrofit Technology: An Analysis of the Cost Effectiveness of Reducing Particulate Matter Emissions from Heavy-Duty Diesel Engines Through Retrofits". EPA's Office of Transportation and Air Quality evaluated the cost and emissions benefits of retrofitting school buses, freight trucks, and bulldozers with catalyzed diesel particulate filters (CDPF) and diesel oxidation catalysts (DOCs), two of the technologies most often used to reduce PM. The report can be located at:

State Assumption of Responsibility for Categorical Exclusions Under NEPA. FHWA recently released guidance on implementing Section 6004 of SAFETEA-LU: "State Assumption of Responsibility for Categorical Exclusions." SAFETEA-LU allows state DOTs to assume project-level environmental responsibilities including the responsibility to make project-level conformity determinations. For more information see:

AMPO Air Quality Group Meeting in Oakland, CA. On April 3 and 4 the AMPO Air Quality Group met at the Metropolitan Transportation Commission (MTC) in Oakland, CA. Fourteen MPOs were represented as well as EPA, FHWA, and AMPO representatives. The meeting included discussion about the SAFETEA-LU Interim Guidance, EPA rulemakings, PM Hot-Spot analysis, diesel retrofits and general information sharing. Another highlight of the meeting was a tour of a local diesel retrofit facility and of retrofitted transit buses and refuse trucks. For more information see:

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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