The Federal Highway Administration has repealed a final rule that required state departments of transportation and metropolitan planning organizations to establish declining carbon dioxide (CO2) targets for greenhouse gas (GHG) emissions measures and report on progress toward the achievement of the target.

The Biden Administration final rule, which was never implemented, would have mandated that state DOTs and MPOs assess the performance of the National Highway System under the National Highway Performance Program by establishing declining CO2 emissions targets and measuring and reporting on the percent change in tailpipe CO2 emissions on the NHS from the calendar year 2022 (also referred to as the Greenhouse Gas or GHG measure).

The Trump Administration has now repealed this final rule, effective May 19, 2025. The Trump Administration asserts that repeal will alleviate a burden on state DOTs and MPOs that, had it been implemented, would have imposed costs with no predictable level of benefits and without clear legal authority. This final rule does not prohibit state DOTs and MPOs from choosing voluntarily to measure and assess CO2 on the NHS or other roads.

Moreover, the notice explained that FHWA does not have legal discretion to allow the GHG measure to become effective. Specifically, two U.S. District Courts held that FHWA exceeded its statutory authority in promulgating the 2023 GHG rule or that the rule was arbitrary and capricious, the rule has been vacated, and appeals of those decisions have been dismissed.