The Trump administration has begun the process of rolling back federal fuel-efficiency regulations that apply separately to truck engines and other individual vehicle components, marking a significant shift in the way future Class 8 trucks could be engineered to comply with U.S. efficiency standards.
The White House argues that the National Highway Traffic Safety Administration (NHTSA) exceeded its legal authority under a regulatory framework expanded during the Obama administration in 2016.
In a new interpretation of federal law announced Friday, NHTSA said its authority should be limited to regulating the fuel efficiency of complete medium- and heavy-duty vehicles rather than individual components such as engines, transmissions, tires and other equipment.
The move does not eliminate federal fuel-efficiency requirements for commercial trucks. Instead, it would give manufacturers greater freedom to decide how an entire vehicle meets those requirements, whether through improvements to engines, transmissions, aerodynamics, cab designs, tires or other technologies.
“The Trump Administration is getting out of the way so manufacturers can decide how they want to meet fuel efficiency requirements,” NHTSA Administrator Jonathan Morrison said in a statement.
According to Morrison, bringing the program into line with the administration’s interpretation of federal law could reduce commercial truck prices and support U.S. manufacturers. However, NHTSA did not provide an estimate of the potential reduction in the cost of new trucks.
The new interpretive rule directly targets regulations developed under the Obama administration as part of a broader federal effort to reduce fuel consumption and greenhouse gas emissions from commercial vehicles.
A Regulatory Debate Rooted in the Bush Administration
Although the regulations being challenged were significantly expanded under President Barack Obama, the origins of the federal fuel-efficiency program date back to the administration of President George W. Bush.
The Energy Independence and Security Act of 2007, signed into law by Bush, instructed NHTSA to create a program aimed at improving fuel efficiency in medium- and heavy-duty commercial vehicles.
The Obama administration began implementing that mandate in 2011 before expanding the program through the Phase 2 greenhouse gas and fuel-efficiency standards, which were jointly finalized by NHTSA and the Environmental Protection Agency in 2016.
Those Phase 2 regulations established standards covering combination tractors, trailers, heavy-duty pickups and vans, vocational vehicles, as well as certain engines used in tractors and vocational trucks. The program was designed to reduce both fuel consumption and greenhouse gas emissions through model year 2027.
At the time, federal regulators estimated that the regulations would save truck owners approximately $170 billion in fuel costs over the lifetime of the program.
They also projected that purchasers of new long-haul trucks in 2027 could recover the additional cost of fuel-saving technologies in less than two years through lower fuel expenses.
The standards were intended to accelerate the deployment of a broad range of technologies, including more efficient engines and powertrains, aerodynamic equipment and lighter-weight components.
Once fully implemented, regulators estimated that tractors could achieve up to 25% lower fuel consumption and carbon dioxide emissions compared with equivalent 2018 models.
Trump Administration Questions NHTSA’s Authority Over Individual Components
Friday’s action is based largely on a legal distinction between regulating an entire commercial vehicle and regulating the individual components used to build it.
NHTSA said the Energy Independence and Security Act authorizes the agency to establish a fuel-efficiency program for commercial vehicles. However, unlike the Clean Air Act, which explicitly gives the Environmental Protection Agency authority over engine emissions, EISA does not specifically grant NHTSA the authority to regulate engines or components such as transmissions and tires.
The agency also pointed to the U.S. Supreme Court’s 2024 decision in Loper Bright Enterprises v. Raimondo, which overturned the Chevron doctrine, the long-standing legal standard that has guided courts’ deference to federal agencies when interpreting ambiguous laws.
NHTSA also cited a recent ruling by the U.S. Court of Appeals for the D.C. Circuit, which the agency said concluded that it lacks authority to regulate the fuel efficiency of components that are not vehicles themselves.
Under the agency’s new interpretation, regulators would still be able to establish fuel-efficiency requirements for completed commercial vehicles while allowing manufacturers more flexibility in choosing the technologies used to meet those targets.
Industry Had Previously Called for Greater Flexibility
The Trump administration’s renewed emphasis on manufacturer flexibility reflects concerns expressed by parts of the trucking and manufacturing industries when the Phase 2 standards were introduced nearly a decade ago.
Industry reaction to the final 2016 rule was generally positive. However, fleets and manufacturers stressed the importance of keeping compliance costs under control and providing sufficient time for the development and deployment of new technologies.
Officials from the American Trucking Associations were described as “cautiously optimistic” when the standards were finalized. The ATA said regulators had addressed concerns related to technology-development lead times and flexibility, while also warning that the success of the program would ultimately depend on fleets’ willingness to purchase and adopt the new technologies.
Daimler Trucks North America also supported the objectives of the Phase 2 program but argued that the regulations should establish long-term targets for the entire vehicle rather than concentrating exclusively on the engine.
The company also emphasized the need to give manufacturers and customers sufficient flexibility to determine economically viable ways of achieving the required targets.
Other manufacturers supported the broader efficiency goals as well.
Paccar said it would comply with the standards while continuing to provide fuel-efficient Kenworth and Peterbilt trucks. Volvo Group North America described improved fuel economy as an objective capable of bringing stakeholders together, while also acknowledging that the targets represented a significant challenge for the industry.
Greater Flexibility Could Also Bring Trade-Offs
The regulatory shift could nevertheless have consequences beyond upfront equipment costs.
Engine-specific standards were originally designed to accelerate the deployment of technologies capable of reducing diesel consumption and greenhouse gas emissions.
EPA and NHTSA previously estimated that the broader Phase 2 program would save truck owners approximately $170 billion in fuel costs and reduce carbon dioxide emissions by around 1.1 billion metric tons over the lifetime of the covered vehicles.
Eliminating NHTSA’s engine-level requirements could provide manufacturers with greater engineering flexibility and potentially reduce the initial cost of equipment.
However, the long-term impact on fuel consumption and emissions will depend largely on how the agency designs and structures its future vehicle-level standards.
Existing Standards Remain in Place for Now
Friday’s action does not immediately repeal the current medium- and heavy-duty vehicle standards.
According to NHTSA, the interpretive rule establishes the legal basis for a future notice-and-comment rulemaking process that would formally reset the agency’s medium- and heavy-duty vehicle program.
Until that regulatory process is completed, the agency said it will exercise its enforcement authority in a manner consistent with its new interpretation of federal law.
The move specifically concerns NHTSA’s authority over fuel efficiency. It does not, by itself, remove the Environmental Protection Agency’s separate authority under the Clean Air Act to regulate emissions from heavy-duty engines.
