49 U.S.C. § 304a

(a) In General .— In preparing a final environmental impact statement under the National Environmental Policy Act of 1969 ( 42 U.S.C. 4321 et seq.), if the lead agency modifies the statement in response to comments that are minor and are confined to factual corrections or explanations of why the comments do not warrant additional agency response, the lead agency may write on errata sheets attached to the statement, instead of rewriting the draft statement, subject to the condition that the errata sheets— (1) cite the sources, authorities, and reasons that support the position of the agency; and (2) if appropriate, indicate the circumstances that would trigger agency reappraisal or further response. (b) Single Document .— To the maximum extent practicable, the lead agency shall expeditiously develop a single document that consists of a final environmental impact statement and a record of decision, unless— (1) the final environmental impact statement makes substantial changes to the proposed action that are relevant to environmental or safety concerns; or (2) there is a significant new circumstance or information relevant to environmental concerns that bears on the proposed action or the impacts of the proposed action. (c) Adoption and Incorporation by Reference of Documents.— (1) Avoiding duplication .— To prevent duplication of analyses and support expeditious and efficient decisions, the operating administrations of the Department of Transportation shall use adoption and incorporation by reference in accordance with this subsection. (2) Adoption of documents of other operating administrations .— An operating administration or a secretarial office within the Department of Transportation may adopt a draft environmental impact statement, an environmental assessment, or a final environmental impact statement of another operating administration for the use of the adopting operating administration when preparing an environmental assessment or final environmental impact statement for a project without recirculating the document for public review, if— (A) the adopting operating administration certifies that the proposed action is substantially the same as the project considered in the document to be adopted; (B) the other operating administration concurs with such decision; and (C) such actions are consistent with the requirements of the National Environmental Policy Act of 1969 ( 42 U.S.C. 4321 et seq.). (3) Incorporation by reference .— An operating administration or secretarial office within the Department of Transportation may incorporate by reference all or portions of a draft environmental impact statement, an environmental assessment, or a final environmental impact statement for the use of the adopting operating administration when preparing an environmental assessment or final environmental impact statement for a project if— (A) the incorporated material is cited in the environmental assessment or final environmental impact statement and the contents of the incorporated material are briefly described; (B) the incorporated material is reasonably available for inspection by potentially interested persons within the time allowed for review and comment; and (C) the incorporated material does not include proprietary data that is not available for review and comment.