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Transportation Conformity Highlights

April 2007

Prepared by the Office of Natural and Human Environment Federal Highway Administration

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EPA Releases Proposed Rule on Transportation Conformity Amendments in SAFETEA-LU.On April 18 EPA issued the proposed conformity rule changes, which make the rule consistent with the Clean Air Act as amended by SAFETEA-LU in August 2005. These include changes in frequency requirements for conformity, a conformity lapse grace period, streamlining of the conformity SIP requirements, and provisions on the substitution of transportation control measures in approved SIPs. The proposed rule also includes other changes including updating terms and minor clarifications to ensure the rule is consistent with other EPA and DOT regulations. Comments will be due 30 days after publication in the Federal Register. Documents can be found at:

EPA Releases Final Rule on Implementation of 1997 PM2.5 Standard.On April 25, the Federal Register included EPA's Final Rule on implementation of the 1997 PM2.5 standard. This rule applies to all 39 areas designated as PM2.5 nonattainment areas effective April 5, 2005. The Final Rule is effective on May 29, 2007. Documents can be found at:

EPA Releases Guidance on Transportation Conformity and the Revised 24-hour PM2.5 Standard.On April 16 EPA released guidance on the implementation of the revised 24-hour PM2.5 standard. The guidance indicates that the 1997 24-hour PM2.5 standards apply until one year after the effective designation date under the new 24-hour PM2.5 standard (the annual PM2.5 standard was not revised in the October 2006 final rule). PM2.5 designations pursuant to the October 2006 final rule are planned to become effective in 2010, this would mean that conformity for the new PM2.5 24-hour would apply in 2011. The guidance does not address the October 2006 revisions to the PM10 standards, which will be addressed by EPA in the future. The guidance memo will be posted at:

EPA Releases Final Clean Air Fine Particle Implementation Rule. On March 29 EPA issued a final rule defining requirements for state implementation plans to clean the air in PM2.5 nonattainment areas. PM2.5 SIPs are due in April 2008 and states must meet the PM2.5 standard by 2010. However, states may propose an attainment date extension for up to five years but not later than 2015. Key issues addressed in the rule include Reasonably Available Control Measures (RACM) and Reasonably Available Control Technologies (RACT) requirements, attainment demonstrations and modeling, and policies on PM2.5 precursors. The rule does not include new source review (NSR) requirements for the PM2.5 standard; these requirements will be addressed in a separate rulemaking. For more information, see:

U.S. Supreme Court Ruling on Greenhouse Gas Emissions.On April 2 The Supreme Court ruled that the U.S. EPA does have the statutory authority to regulate emissions of greenhouse gases from new motor vehicles. Additionally, the Court said that EPA cannot avoid its statutory obligation by noting the uncertainty of various features of climate change and concluding that it would therefore be better not to regulate at this time. EPA and other federal agencies are in the process of determining next steps. It is unclear at this time whether this ruling will impact the transportation conformity process. For more information, see:

NMIM Update: Nonroad Diesel Retrofits Affect Gasoline Engine Evaporative Emissions. On April 2 EPA announced that some potential important information is missing from the NONROAD2005 User Guide regarding the use and limitations of the Daily Temperature & RVP input data file. This relates to EPA's NMIM model because NMIM is not designed to make use of this Daily Temperature & RVP feature of the NONROAD model. NMIM inherently runs NONROAD on a monthly basis and applies the temperatures and fuel properties (such as RVP) by county from the NMIM County Database. More information can be found at:


Transportation and Air Quality Committee Summer Meeting - July 9-11. 2007.The Transportation Land-Use, Development and Air Quality Conference will be held in Orlando, Florida in July 2007. This conference is co-chaired by several organizations and will be held in conjunction with the summer meeting of the Transportation and Air Quality Committee. The conference price is tentatively set at $250. For more information, see:

STAQS Conference Scheduled. The Southern Transportation and Air Quality Summit 2007 is an event sponsored by the FHWA and EPA Regions 3, 4, and 6. It will be held August 28-30, 2007 in Savannah, Georgia, at the Hilton Savannah DeSoto Hotel. The purpose of the summit is to bring together stakeholders from both the transportation and air quality communities to discuss current and coming regulatory environment, technologies and current practices vital to the field of air quality and transportation. The summit is geared to practitioners involved with public agencies at all levels. A host of speakers from within the southern and eastern regions will present a number of key topics, best practices and latest information vital to transportation, planning, and air quality professionals. Contact: Mike Roberts, 404-562-3928,

Training Opportunities

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 is available at: For further information, contact: Mike Roberts at 404-562-3928 or at

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FHWA Resource Center Air Quality Team Contacts:

Updated: 10/20/2015
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