NAAQS and Designations
The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for pollutants considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. The EPA Office of Air Quality Planning and Standards (OAQPS) has set National Ambient Air Quality Standards for six principal pollutants (Particulate Matter, Ozone, Carbon Monoxide, Nitrogen Dioxide, Lead, Sulfur Dioxide), which are called "criteria" pollutants. Transportation conformity applies to particulate matter, ozone, carbon monoxide, and nitrogen dioxide.
Policy & Guidance
Ozone
Particulate Matter
- Transportation Conformity Guidance for Quantitative Hot-spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas (EPA, December 2010) - Guidance for modeling the local air quality impacts of certain transportation projects on the PM2.5 and PM10 national ambient air quality standards (NAAQS). This guidance is to be used by state and local agencies to conduct quantitative PM “hot-spot analyses” for new highway and transit projects that involve significant diesel emissions.
Main document only
Appendices only
Fact Sheet (HTML) or (PDF)
- Using MOVES in Project-Level Carbon Monoxide Analyses (EPA, December 2010) - This guidance describes how to use the MOVES emissions model to estimate CO emissions from transportation projects, including roadway intersections, highways, transit projects, parking lots and intermodal terminals.
- Federal Register Notice of Availability: Official Release of the MOVES2010a and EMFAC2007 Motor Vehicle Emissions Models for Transportation Conformity Hot-Spot Analyses and Availability of Modeling Guidance (December 2010) – This notice approves MOVES2010a for PM and CO hot-spot analyses (and EMFAC2007 for PM hot-spot analyses in California) with a 2-year conformity grace period. EPA also announced the availability of its final PM hot-spot guidance and CO project-level MOVES guidance.
- Clarification to the "Transportation Conformity Guidance for Qualitative Hot-spot Analysis in PM2.5 and PM10 Nonattainment and Maintenance Areas" (February 2009)
- Policy Guidance on Use of November 2006 Update to AP-42 for Re-entrained Road Dust for SIP Development and Transportation Conformity (August 2007) - EPA guidance on changes made to the AP-42 methods for road dust and how and when to use them in PM2.5 SIPs and transportation conformity determinations. This guidance supersedes the AP-42 portions of EPA's February 2004 guidance, which addressed both MOBILE6.2 and AP-42. The portions of the February 2004 guidance addressing MOBILE6.2 remain in effect.
- Area Designations for the Revised 24-hour Fine Particle National Ambient Air Quality Standard (June 2007) - EPA guidance on the timeline for designating areas for the purpose of implementing the revised PM2.5 NAAQS
- Transportation Conformity and the Revised 24-hour PM2.5 Standard (April 2007) - EPA guidance that addresses how transportation conformity will be implemented under the revised 24-hour PM2.5 standard
- Transportation Conformity Guidance for Qualitative Hot-Spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas (March 2006) - Memorandum from FHWA and EPA on how to perform qualitative hot-spot analyses in PM2.5 and PM10 nonattainment and maintenance areas, as required by the March 10, 2006, final transportation conformity rule.
- Transportation Conformity Alert to FHWA Divisions on PM2.5 Project-Level Conformity (November 2005) - Alert to FHWA Divisions concerning PM2.5 Project-Level Conformity requirements as of April 5, 2006.
- Guidance for Creating Annual On-Road Mobile Source Emission Inventories for PM2.5 Nonattainment Areas for Use in SIPs and Conformity (August 2005) - EPA guidance on preparation of annual inventories for PM2.5 SIPs or regional conformity analyses by state and local agencies. It also addresses the possible use of the National Mobile Inventory Model (NMIM) in SIPs and conformity analyses.
- Guidance for Determining the "Attainment Years" for Transportation Conformity in New 8-Hour Ozone and PM2.5 Nonattainment Areas (March 2005) - EPA guidance for 8-hour ozone and PM2.5 nonattainment areas in selecting attainment dates for use in transportation conformity determinations both before and after SIPs are submitted. It also describes some flexibilities that are available to areas using interim emission or budget tests in choosing which years to perform a regional emissions analysis.
- Conformity Information to Inform PM-2.5 Designations (October 2004) - EPA guidance on the transportation conformity burden associated with designating areas for the PM2.5 air quality standard.
- Designations for the Fine Particle National Ambient Air Quality Standards (April 2003) - EPA guidance on the process for designating areas for the purpose of implementing the PM2.5 NAAQS
- Guidance for Qualitative Project Level "Hot-Spot" Analysis in PM10 Nonattainment and Maintenance Areas (September 2001) - FHWA guidance (and accompanying examples) for conducting PM10 qualitative hot-spot analyses - note this guidance pertains only to those hot-spot analyses begun prior to March 29, 2006.
- Information: Limited Maintenance Plans (September 2001) - Memorandum from EPA detailing instances when moderate PM10 nonattinment areas can be redesignated to attainment with a streamlined maintenance plan.
