Section 176(c) of the Clean Air Act (CAA) states that actions of the federal government may not cause or contribute to new violations of the CAA, nor may they increase the frequency or severity of existing violations, nor delay the attainment of a standard in a nonattainment area, and all actions must conform to the state SIP's purpose of eliminating or reducing the severity and number of violations of the National Ambient Air Quality Standards (NAAQS) and achieving expeditious attainment of such standards.

The purpose of Ohio's transportation conformity SIP is to ensure that any transportation plan developed under title 23 of the U.S. code or Chapter 53 of Title 49 of the U.S. Code for implementation in the state of Ohio, conforms to Ohio's SIP and fulfills the requirements of Section 176(c) of the CAA.