Trailer designs play a role in fuel economy, but U.S. regulators seem ready to abandon the stalled rules that would have required trailer updates in the name of reducing greenhouse gases (GHG).

In a bulletin to members on April 17, the Canadian Transportation Equipment Association (CTEA) cited a related reference on page 311 of the U.S. Environmental Protection Agency’s proposal for a third phase of greenhouse gas emissions standards.

“As part of the HD [heavy-duty] GHG Phase 2 rulemaking, we set standards for certain types of trailers used in combination with tractors (see 81 FR 73639, October 25, 2016),” the EPA text says. “We are proposing to remove the regulatory provisions related to trailers in 40 CFR part 1037 to carry out a decision by the U.S. Court of Appeals for the D.C. Circuit, which vacated the portions of the HD GHG Phase 2 final rule that apply to trailers.”

If such rules were applied, trailer manufacturers would need to adopt fuel-saving technologies like side skirts and automatic tire pressure monitoring systems, to help overall tractor-trailers reach their Phase 2 emissions targets.

Those U.S. trailer rules were originally set to take hold January 2020, but were challenged by the Truck Trailer Manufacturers Association. The U.S. Court of Appeals for the D.C. Circuit ultimately determined the EPA an the U.S. National Highway Traffic Safety Administration (NHTSA) couldn’t apply the rules because trailers are not “motor vehicles”.

Just weeks ago, Canada’s federal government suspended proposed GHG emissions standard for trailers by up to one additional year in the face of stalled U.S. rules.

Stephane Couroux, director of Environment and Climate Change Canada’s transportation division, said at the time that the department was consulting stakeholders and would continue to monitor the situation in the U.S.

Canadian emissions standards typically mirror those established south of the border.