The National Highway Traffic Safety Administration (NHTSA) is scaling back its authority to regulate fuel economy standards for commercial truck engines, reversing its own Obama-era policy to eliminate engine-only regulations.
Industry groups had previously pushed back against standalone engine rules during public comment periods, arguing NHTSA was overstepping its statutory limits by dictating engine components rather than whole-vehicle metrics.
NHTSA ultimately agreed. In an interpretive rule scheduled for publication Monday in the Federal Register, NHTSA said it lacks the legal authority to set fuel efficiency rules for heavy-duty truck engines independent of the vehicles themselves.
Under the new interpretation, NHTSA will continue to mandate fuel efficiency improvements for complete vehicles and work trucks, but will leave the specific engine design and powertrain choices entirely up to manufacturers. The agency said the rollback gives commercial truck manufacturers greater flexibility in how they meet overarching vehicle fuel economy standards, allowing them to tailor engineering decisions to the specific needs of their commercial buyers.
NHTSA previously asserted that the Energy Independence and Security Act of 2007 (EISA) granted it broad authority to regulate truck engines separately from the entire vehicle, but Friday walked that back.
"EISA requires NHTSA to set fuel economy standards for medium- and heavy-duty on-highway vehicles and work trucks but did not authorize NHTSA to set standards for engines on a standalone basis," NHTSA said in reconsidering its stance.
The regulatory pullback aligns with the Trump administration's deregulatory agenda. The Federal Register notice outlines compliance with recent executive orders focused on "Unleashing Prosperity Through Deregulation" and implementing initiatives from the president's newly formed "Department of Government Efficiency."
The interpretive rule applies immediately upon publication on Aug. 31.
