NHTSA Moves to Scrap Truck Fuel Economy Standards

The National Highway Traffic Safety Administration is moving to narrow its authority over fuel-efficiency standards for standalone medium- and heavy-duty truck engines, reversing the agency’s prior interpretation of its regulatory power. Existing commercial vehicle fuel-efficiency standards remain in place while NHTSA develops a final rule.

NHTSA Reconsiders Engine-Only Authority

NHTSA said it has reconsidered whether federal law allows the agency to set fuel-economy standards for medium- and heavy-duty engines separately from the vehicles in which they are installed.

The action reverses an Obama-era policy adopted as part of the agencies’ broader approach to regulating commercial vehicle efficiency. Under the revised interpretation, NHTSA said its authority does not extend to establishing standalone fuel-economy requirements for truck engines.

The agency’s position relies in part on a 2021 decision by the U.S. Court of Appeals for the District of Columbia Circuit involving trailer standards. In that case, the court found that trailers do not burn fuel and questioned whether they could be treated as vehicles for fuel-economy purposes. NHTSA is applying similar reasoning to engines, which do not operate as complete vehicles independently of the trucks that use them.

Manufacturers Seek Greater Design Flexibility

The Truck and Engine Manufacturers Association welcomed the review, saying manufacturers need flexibility to meet efficiency goals through a combination of technologies and vehicle design changes.

“EMA looks forward to working with NHTSA as the agency develops a final rule addressing fuel efficiency standards for medium- and heavy-duty vehicles that reflect real-world customer adoption of fuel-saving technologies, deliver meaningful operational and economic benefits to customers, and provide manufacturers the flexibility to develop engines and vehicles that meet the diverse demands of the commercial vehicle market,” the association said.

Industry groups have argued that efficiency improvements can come from multiple areas, including aerodynamics, vehicle weight, tires, transmissions and engine design. They contend that focusing too narrowly on engine performance could limit equipment specifications available to trucking fleets and other commercial vehicle operators.

Phase 2 Program Remains in Focus

The review affects the regulatory structure for truck and engine efficiency standards, but current requirements remain in effect during the rulemaking process. NHTSA and the Environmental Protection Agency previously estimated that the broader Phase 2 program would save truck owners approximately $170 billion in fuel costs and reduce carbon dioxide emissions by about 1.1 billion metric tons over the lifetime of covered vehicles.

The administration has also proposed changes to fuel-economy requirements for passenger cars and light trucks through model year 2031. Those proposals are separate from the agency’s reconsideration of its authority over standalone commercial truck engines.

Reaction Centers on Costs and Fuel Exposure

Supporters of the NHTSA action say manufacturers should be allowed to determine how best to meet fuel-efficiency requirements across complete vehicle systems. Critics, including electrification advocates, argue that weaker or narrower standards could slow efficiency improvements and leave trucking companies more exposed to diesel-price volatility.

NHTSA Administrator Jonathan Morrison said the agency’s approach would give manufacturers more control over how they design engines and vehicles while meeting applicable fuel-efficiency requirements. The agency is expected to address the scope of its authority and the future regulatory framework in a final rule.