In this action, EPA is amending the transportation conformity rule to finalize provisions that were proposed on May 15, 2009. These amendments primarily affect conformity's implementation in PM<INF>2.5</INF> and PM<INF>10</INF> nonattainment and maintenance areas. EPA is updating the transportation conformity regulation in light of an October 17, 2006 final rule that strengthened the 24-hour PM<INF>2.5</INF> national ambient air quality standard (NAAQS) and revoked the annual PM<INF>10</INF> NAAQS. In addition, EPA is clarifying the regulations concerning hot-spot analyses to address a December 2007 remand from the Court of Appeals for the District of Columbia Circuit. This portion of the final rule applies to PM<INF>2.5</INF> and PM<INF>10</INF> nonattainment and maintenance areas as well as carbon monoxide nonattainment and maintenance areas. The Clean Air Act (CAA) requires federally supported transportation plans, transportation improvement programs, and projects to be consistent with ("conform to") the purpose of the state air quality implementation plan. The U.S. Department of Transportation (DOT) is EPA's federal partner in implementing the transportation conformity regulation. EPA has consulted with DOT, and they concur with this final rule.