NHTSA now says it never had the power to set fuel economy standards for heavy truck engines, which is the argument Volvo and Daimler made in 2011 and lost

Volvo and Daimler made this argument in 2011. The National Highway Traffic Safety Administration rejected it then, in the final rule that created the programme, and on Friday morning it adopted it.

The interpretive rule filed at a quarter to nine says that the Energy Independence and Security Act of 2007 required the agency to set fuel economy standards for commercial medium and heavy-duty on-highway vehicles and work trucks, and did not authorise it to set standards for engines on their own. The Clean Air Act names engines. The 2007 statute names vehicles. That is the whole of it.

What the agency said the first time

In the Phase 1 rulemaking that produced the programme in 2011, NHTSA set standards for engines used in combination tractors and vocational vehicles. Its authority to do so rested on the statutory power to prescribe separate standards for different classes of vehicles, which the agency then said it read broadly to reach engines. Its own words, in the final rule at 76 FR 57112, were that it interpreted the phrase "broadly to allow regulation of HD engines in addition to HD vehicles".

Volvo and Daimler filed comments saying the statute reached completed vehicles only. NHTSA answered that the language "does not . . . preclude[] the regulation of engines, but rather explicitly leaves the regulatory approach to the agency's expertise and discretion". Phase 2 in 2016 raised the stringency and referred back to that footnote for its authority.

Friday's document quotes all of it, including its own broad-reading admission, and then says the text speaks only of vehicles.

The sentence that does the work

Two sentences sit a paragraph apart near the end of section III and they have to be read together.

The first: "This interpretation does not change existing standards or any rights or obligations under the MDHD program."

The second: "Pending the rulemaking process, NHTSA will exercise its enforcement authority with regard to affected standards in accordance with the interpretation set forth in this rule."

Nothing is repealed. The engine standards stay in parts 523, 534 and 535 until a notice-and-comment rulemaking removes them. The agency has simply said how it will enforce them in the interval, which is in accordance with a reading under which it never had the power to issue them.

How it was issued

The rule took no comment and gets no waiting period. NHTSA relied on 5 U.S.C. 553(b)(A) to skip notice and comment as an interpretive rule, and on 553(d)(2) to skip the 30-day delay. It is applicable the day it publishes, which is Monday.

The Office of Information and Regulatory Affairs designated it a significant regulatory action under Executive Order 12866, so it went to OMB for review, and the document states that there are no costs or benefits associated with it. It is not a major rule under the Congressional Review Act. For environmental purposes the agency states that this is not a final agency action within the meaning of chapter 5 of title 5, which is also the reason no environmental document was prepared.

The other half of the engine

EPA regulated the same engines under the Clean Air Act, and its authority to do so was never in doubt, because the statute says engines. In February this year EPA rescinded the 2009 endangerment finding and repealed the greenhouse gas standards for light, medium and heavy-duty vehicles and engines. The 2023 NOx standards for heavy-duty engines remain, take effect in model year 2027, and are themselves under a proposal to amend.

NHTSA says one of the matters it will consider in resetting the programme is the relationship between those NOx reductions and fuel consumption.

Jonathan Morrison signed the rule on Thursday.