Transportation Conformity

Transportation Conformity

Transportation conformity is a process that links a state's air quality efforts with its transportation planning activities. It requires multiple agencies and groups to work together to ensure that federal transportation dollars go to projects that are consistent with a state's air quality goals.

As part of transportation conformity, emissions analyses must be conducted for every proposed transportation plan, program or project in a nonattainment area. An emission analysis estimates the mobile source emissions that will likely result if a project is carried out. Analyses use the latest planning assumptions, traffic modeling, and federally approved emissions models.

The process is meant to ensure that new projects will not produce new air quality violations, worsen existing violations, or delay the timely attainment of air quality standards. For a project to receive federal funds, it must be shown that emissions resulting from it will not exceed the area's emissions budget. The budget is part of the state's air quality plan, also known as the State Implementation Plan (SIP). The federal government cannot fund or approve transportation plans, programs or projects that do not conform to the SIP.

As the state's air quality planning agency, DHEC developed and is responsible for updating South Carolina's Transportation Conformity SIP in consultation with transportation agencies and air quality partners.

Who should be concerned?

  • Elected officials
  • Federal, state and local agencies responsible for planned growth, economic development, environmental protection, transportation, land use management, natural resources and historic preservation.
  • Members of the local Chamber of Commerce
  • Local homebuilding associations
  • Regional building industry organizations
  • Anyone involved in a project defined as regionally significant *
  • Transportation agencies
  • Organizations/agencies representing users of public transportation
  • Organizations/agencies representing those with special needs
  • Homeowners' associations

* Regionally significant project means a transportation project (other than an exempt project) that is on a facility which serves regional transportation needs and would normally be included in the modeling of a metropolitan area's transportation network, including at a minimum all principal arterial highways and all fixed guideway transit facilities that offer an alternative to regional highway travel. Examples of regionally significant transportation projects would be those that offer access to and from the area outside of the region, major activity centers in the region, major planned developments such as new retail malls, sports complexes, etc., or transportation terminals as well as most terminals themselves.

Why be concerned about transportation conformity?

If a metropolitan planning organization (MPO) and interagency consultation partners are unaware of a regionally significant project and, as a result, leave the project out of the area's long range transportation plan (LRTP) or transportation improvement program (TIP), an amendment must be made to the plan and a conformity analysis performed. This can result in significant project delays, whether or not federal funds are involved in the project.

What transportation activities are subject to conformity?

  • Long Range Transportation Plan - Planning for a 20-year timeframe
  • Transportation Improvement Program - Planning for a four-year timeframe.
  • The first two years of the TIP are limited to those projects for which funding is available or committed.
  • Projects included in the second two years of the TIP must have funding reasonably available.
  • Federal projects that:
    • Receive funding under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU)
    • Require Federal Highway Administration (FHWA) and/or Federal Transit Authority (FTA) approval
  • Regionally significant non-federal projects.

What is a conformity lapse?

If transportation conformity is not met according to plan, a conformity lapse occurs. This limits an area's federal transportation funding to safety projects, certain mass transportation projects, transportation control measures from an approved SIP, and project phases that were authorized by the FHWA/FTA prior to the lapse.

Related Documents, Links


Holly Randolph, (803) 898-2470

Carla Bedenbaugh, (803) 898-4279