In January 2017, the Federal Highway Administration within the Transportation Department published a rule commonly known as the GHG Measure, under the full name "Assessing Performance of the National Highway System, Freight Movement on the Interstate System, and Congestion Mitigation and Air Quality Improvement Program."
The GHG Measure required states, beginning in February 2017, to do the following:
- Track on-road greenhouse gas emissions
- Set locally-appropriate performance targets
- Ensure consistency in data collection
The Trump administration has repeatedly attempted to block the rule from coming into force. In the spring of 2017, the Environmental Protection Agency twice delayed the effective date of the GHG Measure until May 2017. The administration announced an indefinite delay of the rule in May 2017.
In September 2017, eight attorneys general sued the Trump administration for unlawfully delaying and suspending the effective date of on-road greenhouse gas emissions data requirements. The lawsuit prompted the Transportation Department to immediately reverse course and begin to implement required data collection procedures. The department subsequently published a notice of proposed rulemaking to repeal the GHG Measure. Six attorneys general, led by California Attorney General Xavier Becerra, filed comments in November 2017 opposing the proposed repeal.
In May 2018, the Transportation Department issued a final rule that repealed the GHG Measure.