40 CFR § 93.116 - Criteria and procedures: Localized CO, PM10, and PM2.5 violations (hot-spots).
(a) This paragraph applies at all times. The FHWA/FTA project must not cause or contribute to any new localized CO, PM10, and/or PM2.5 violations, increase the frequency or severity of any existing CO, PM10, and/or PM2.5 violations, or delay timely attainment of any NAAQS or any required interim emission reductions or other milestones in CO, PM10, and PM2.5 nonattainment and maintenance areas. This criterion is satisfied without a hot-spot analysis in PM10 and PM2.5 nonattainment and maintenance areas for FHWA/FTA projects that are not identified in § 93.123(b)(1). This criterion is satisfied for all other FHWA/FTA projects in CO, PM10 and PM2.5 nonattainment and maintenance areas if it is demonstrated that during the time frame of the transportation plan no new local violations will be created and the severity or number of existing violations will not be increased as a result of the project, and the project has been included in a regional emissions analysis that meets applicable §§ 93.118 and/or 93.119 requirements. The demonstration must be performed according to the consultation requirements of § 93.105(c)(1)(i) and the methodology requirements of § 93.123.
(b) This paragraph applies for CO nonattainment areas as described in § 93.109(d)(1). Each FHWA/FTA project must eliminate or reduce the severity and number of localized CO violations in the area substantially affected by the project (in CO nonattainment areas). This criterion is satisfied with respect to existing localized CO violations if it is demonstrated that during the time frame of the transportation plan (or regional emissions analysis) existing localized CO violations will be eliminated or reduced in severity and number as a result of the project. The demonstration must be performed according to the consultation requirements of § 93.105(c)(1)(i) and the methodology requirements of § 93.123.