Transportation conformity is required to ensure that Federal funding and approval goes to transportation activities that are consistent with air quality goals. Conformity applies to transportation plans, transportation improvement programs (TIPs), and projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration (FTA) in areas that do not meet or previously have not met air quality standards for ozone, carbon monoxide, particulate matter, or nitrogen dioxide. These areas are known as "non-attainment areas" or "maintenance areas," respectively.
A conformity determination demonstrates that the total emissions projected for a plan or program are within the emissions limits ("budgets") established by the air quality plan or State Implementation Plan (SIP). The requirement for transportation conformity is established in the United States Code of Federal Regulations (40 CFR 93.104).
Regional emissions are estimated based on highway and transit usage according to transportation plans and TIPs. The projected emissions for the plan and TIP must not exceed the emissions limits (or “budgets") established by the SIP.
The Decision Process
A formal interagency consultation process involving the Environmental Protection Agency (EPA), FHWA, FTA and state and local transportation and air quality agencies is required in developing SIPs, TIPs, and transportation plans, and in making conformity determinations. Metropolitan Planning Organizations (MPO) make conformity determinations in metropolitan areas, while NCDOT does so in areas outside of MPOs. Conformity determinations must also be made at the Federal level by FHWA/FTA. These determinations must be made at least every four years, or when transportation plans or TIPs are updated.
The SIP places limits on emissions of each pollutant for each source type (mobile, stationary and area sources). Projected emissions from highway and transit usage must be less than or equal to the emissions limits for on-road mobile vehicles that are established by the SIP. These emissions limits for motor vehicle emissions sources are called "budgets." Budgets are developed as part of the air quality planning process by State air quality/environmental agencies, and approved by EPA. Transportation agencies participate in this process.
North Carolina non-attainment and maintenance counties for each air quality standard are as follows:
8-HOUR OZONE (2008) Nonattainment Areas:
Charlotte-Rock Hill, NC-SC
Cabarrus County (P)
Gaston County (P)
Iredell County (P)
Lincoln County (P)
Rowan County (P)
Union County (P)
8-HOUR OZONE (1997) Nonattainment Areas^:
Charlotte-Gastonia-Rock Hill, NC-SC (Moderate)
Iredell County (Partial) - Davidson Township, Coddle Creek Township
8-HOUR OZONE (1997) Maintenance Areas^:
Haywood and Swain Cos (Great Smoky National Park)
Haywood County (Partial) – Great Smoky Mountain National Park
Swain County (Partial) – Great Smoky Mountain National Park
Raleigh-Durham-Chapel Hill, NC
Chatham County (Partial) - Baldwin Township, Center Township, New Hope Township, Williams Township
Rocky Mount, NC
^It is anticipated that EPA will revoke the 1997 ozone standard in July 2013.
CARBON MONOXIDE Maintenance Areas:
PM2.5 (1997) Nonattainment Areas:
Greensboro-Winston Salem-High Point, NC