The Federal Highway Administration, Federal Transit Administration, and Federal Railroad Administration joint NEPA regulations (23 CFR part 771) contain a process in 23 CFR 771.129 for re-evaluating environmental documents or decisions to determine whether the original document or decision remains valid, or a supplemental or new analysis (e.g., supplemental environmental impact statement (EIS) or environmental assessment (EA)) is needed. The agencies developed this guidance to provide clarity and consistency to the re-evaluation process consistent with their regulations.