The National Highway Traffic Safety Administration (NHTSA) has issued an interpretive rule reversing a commercial truck engine rule from the Obama era, which had extended regulatory reach to standalone engines beyond NHTSA’s statutory authority. The move cites the US Supreme Court’s Loper Bright Enterprises v. Raimondo ruling, which curtailed agencies’ power to regulate beyond explicit statutory mandates.

The interpretive rule does not itself change existing fuel efficiency standards for medium- and heavy-duty (MDHD) commercial vehicles. Rather, it establishes that NHTSA’s mandate under the Energy Independence and Security Act (EISA) covers vehicle-level fuel efficiency, not standalone engines or components such as transmissions and tyres, with a notice-and-comment rulemaking process to follow.

NHTSA argued that regulating standalone engines constrained manufacturers’ ability to pursue whole-vehicle approaches to fuel efficiency, noting that improvements to cab aerodynamics, tyres and transmissions can be as impactful as engine modifications. The agency said vehicle-level regulation gives companies the flexibility to tailor designs to real-world operational demands.

In a statement, NHTSA Administrator Jonathan Morrison said the rule would lower commercial truck prices and allow American manufacturers and their employees to thrive. Pending the forthcoming rulemaking, the agency will enforce existing standards in line with the new interpretation.

Source: NHTSA