The Safety Grant Consistency Act seeks to regulate the oversight of federal highway safety grant programs, specifically those outlined in sections 402 and 405 of title 23, United States Code. A core provision of the bill is to prohibit the Secretary of Transportation from establishing any new performance measures or regulatory or program requirements for these grants that were not in effect prior to the Act's enactment. Additionally, the legislation mandates that the Secretary must ease or eliminate existing requirements for highway safety grant programs if they are not explicitly authorized or required by an Act of Congress. This measure aims to reduce administrative burdens and ensure that only congressionally approved stipulations govern these critical safety initiatives.