The National Environmental Policy Act (NEPA) is a federal procedural law that establishes a national environmental policy.

Section 101 of NEPA provides a national policy "to use all practicable means and measures, including financial and technical assistance, in a manner calculated to foster and promote the general welfare, to create and maintain conditions under which man and nature can exist in productive harmony, and fulfill the social, economic, and other requirements of present and future generations of Americans." 42 U.S.C. 4331(a).

Section 102 of NEPA establishes procedural requirements, applying that national policy to proposals for major federal actions significantly affecting the quality of the human environment by requiring federal agencies to prepare a detailed statement on: (1) the environmental impact of the proposed action; (2) any adverse effects that cannot be avoided; (3) alternatives to the proposed action; (4) the relationship between local short-term uses of man’s environment and the maintenance and enhancement of long-term productivity; and (5) any irreversible and irretrievable commitments of resources that would be involved in the proposed action. 42 U.S.C. 4332(2)(C).

The Council on Environmental Quality (CEQ) regulations (40 CFR parts 1500-1508) implements section 102(2) of NEPA and provides direction to determine actions subject to procedural requirements.

The Federal Highway Administration (FHWA) issued regulations Environmental Impact and Related Procedures (23 CFR 771) to address the NEPA responsibilities established by CEQ.