D.C. Circuit Invalidates Trailer Emissions Regulations

On November 12, 2021, the U.S. Court of Appeals, D.C. Circuit, overturned an Obama-era emissions rule directed at newly-manufactured trailers.  In order to regulate trailers, either a new regulation will be required, or Congress will need to expressly expand agency authority.   

During the Obama Administration, the Environmental Protection Agency (EPA) promulgated numerous regulations aimed at limiting harmful emissions in various industries and sectors across the country.  One area of emphasis was shipping and trucking, specifically the use of heavy-duty trucks and vans.  In October of 2016, the EPA and the National Highway Traffic Safety Administration (NHTSA) issued a joint final rule, titled “Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles—Phase 2."  81 FR 73478-01 (Oct. 25, 2016). 

As enabling statues, the EPA cited the Clean Air Act, which authorized the EPA to regulate "motor vehicles,"1 while NHTSA cited the Ten-in-Ten Fuel Economy Act, which enabled that agency to regulate "commercial medium-duty or heavy-duty on-highway vehicles."2  Under the jointly created rule, the EPA and NHTSA set greenhouse gas emission and fuel efficiency standards for not only hauling trucks (tractors), but also trailers.  Among other things, the regulation required trailer manufacturers to adopt fuel-efficient technology such as side skirts and automatic tire pressure systems.  Trailer manufacturers brought suit.3

In Truck Trailer Manufacturers Assn., Inc v. Envtl. Protec. Agency,4 the D.C. Circuit held that both agencies had exceeded the authority of their respective enabling statutes, voiding all portions of the rule that apply to trailers.  In a rather straightforward assessment of statutory language, the Court reasoned that trailers could not be a "motor vehicle" under the Clean Air Act because they are not self-propelled and are generally manufactured and sold separately from tractors.5  The majority also reasoned that the Ten-in-Ten Fuel Economy Act does not enable NHTSA to regulate trailers, because trailers do not consume fuel.6  Accordingly, neither the EPA nor NHTSA had the authority to place emission or fuel-based regulations on trailers on manufacturers. 

Judge Millett dissented with respect to NHTSA’s authority.  She reached that conclusion because a trailer fits within the definition of a “vehicle” (trailers are even included in the definition of “motor vehicle” in certain places within the transportation title of the United States Code).  Under her view NHTSA's interpretation was entitled to the Chevron deference, and the majority did not analyze the rulemaking under this framework.7 

While the Court invalidated the trailer rule, the Court indicated a way in which the agencies could regulate trailers: stating "[t]o be sure, NHTSA can regulate tractors based on the trailers they pull, as can the EPA. But neither NHTSA nor the EPA can regulate trailers themselves."8   

If the agencies were so inclined, they might follow the Court’s guidance and regulate tractors in a way that causes trailer manufacturers to adopt fuel-efficient technology over and above – or at a faster rate – than market forces would already dictate.  An alternative would be for Congress to direct the EPA and NHTSA to establish an emissions rule that applies to trailers. 

The House of Representatives passed the Build Back Better Act on Nov. 19, 2021, which addresses climate change among other topics.  That legislation did not address the trailer issue, but the legislation still must pass the Senate.  If it can pass the Senate, the bill is expected to be modified, and would then also be subject to reconciliation.  This would leave a possible opportunity to tuck in statutory language that would clarify NHTSA and the EPA’s authority.  However, because new legislation may not be required if the regulation were crafted differently, there may be less urgency from Congress to include this additional authority to the EPA and NHTSA.  Congressional action is even less likely due to the very narrow path for the Senate to pass a Build Back Better bill.  The agencies may be left to utilize existing statutory authority if they decide to take another shot at regulating trailers pulled by tractors.




1 42 U.S.C.A. § 7521(a)(1).

2 49 U.S.C.A. § 32902(k).

3 Kevin Jones, Court removes trailers from GHG 2, FleetOwner, (Nov. 15, 2021) https://www.fleetowner.com/equipment/trucks-trailers/article/21181209/court-removes-trailers-from-ghg-2 (brief overview of the history of litigation on this matter, beginning in 2016). 

4 Truck Trailer Manufacturers Assn., Inc v. Envtl. Protec. Agency, 16-1430, 2021 WL 5263958 (D.C. Cir. Nov. 12, 2021).

5  Id. at *3-4.

6 Id. at *6.

7 Id. at *11-12.

8 Id. at *8.

Share this post: