Third round of GHG emission rules unveiled by U.S. EPA

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The U.S. Environmental Protection Agency (EPA) is proposing tighter limits on greenhouse gas (GHG) emissions that would apply to Model Year 2028-32 medium- and heavy-duty engines and vehicles. And it’s also looking to reopen rules that were previously established for Model Year 2027.

It represents the third round of GHG limits and builds on NOx limits that were finalized in December. And such rules are typically mirrored by Canadian regulators.

The first phase of GHG rules covered Model Years 2014-18, while Phase 2 applied to Model Years 2021-27.

aerial shot of truck on U.S. bridge
(Photo: iStock)

New proposals that apply to heavy-duty trucks would slash 1.8 billion tons of carbon dioxide through 2055 – the equivalent of eliminating all GHG emissions from today’s U.S. transportation sector for an entire year.

Combined with proposals for light-duty vehicles, the changes would eliminate nearly 10 billion tons of carbon dioxide emissions through 2055, which is double the U.S. total of CO2 emissions in 2022.

The most recent GHG standards are expected to reduce CO2 emissions by 1.1 billion metric tons over the lifetime of new vehicles sold under the program.

CO2 limits

EPA believes the Phase 3 GHG rules are “appropriate and feasible considering cost, lead time, and other factors,” it says in a related regulatory document.

Low-roof Class 8 tractors with sleepers would be capped at 64.1 grams of CO2 per ton mile in 2027, dropping to 48.1 grams in 2032 and later. Mid-roof designs would see limits of 69.6 to 52.2 grams, and high-roof designs would begin at 64.3 grams per ton mile before dropping to 48.2 grams.

Class 8 day cabs would see limits of 66.1 to 70.2 grams per ton mile in 2027, depending on the roof design, ultimately dropping to 48.4 to 51.5 grams in 2032 and later.

“The proposed standards do not mandate the use of a specific technology,” the regulatory document stresses, referring to how transmissions, aerodynamics, engines, battery-electric powertrains and fuel-cell powertrains could be used to hit the targets.

Accelerating zero-emission vehicles

But the rules are expected to drive the widespread use of particulate filters and carbon-dioxide-reducing technologies, while also accelerating the use of zero-emission vehicles.

Zero-emission vehicles (ZEVs) would see changes to warranty requirements for batteries and other components, while state-of-health monitors would be required for plug-in hybrid and battery-electric vehicles.

“Several significant developments have occurred since 2016 that point to ZEV technologies becoming more readily available much sooner than we had previously projected for the HD sector,” the EPA adds, referring to related GHG reductions.

Early ZEV models are expected to expand to more applications, costs are projected to continue to fall, and the cost to manufacture lithium-ion batteries have dropped significantly.

Industry reaction

“Following the 2022 release of EPA’s NOX emissions rule, the GHG Phase 3 rulemaking presents a monumental opportunity to further accelerate the transition of the nation’s trucking fleet to zero-emission vehicles (ZEVs),” Truck and Engine Manufacturers Association president Jed Mandel said in a statement.

 “A thoughtfully crafted GHG Phase 3 rule has the potential to improve the health of our communities, transform commerce, and spur job creation through infrastructure development. EMA member companies already are producing heavy-duty ZEVs and want them deployed on the nation’s roadways as soon as possible.”

“We share the goal of reducing greenhouse gas emissions and improving fuel efficiency and believe any regulation must be practical, achievable, and based on sound science,” said American Trucking Association president and CEO Chris Spear.

“While these standards are directed at manufacturers, it is fleets – the customers and end-users of this equipment – who will ultimately determine their level of success. The Phase 3 standards must take into account the complex challenges and operating conditions facing motor carriers as we manage the transition to a zero-emission future while simultaneously moving more than 72% of the economy’s freight.”

But the ATA president did express disappointment in plans to reopen the Phase 2 regulations. 

“To make the plans and investments necessary for a successful transition, our industry needs regulatory certainty — not whimsical changes of mind from year to year,” Spear said.
“Our industry has always found ways to partner with EPA on regulations that are tough but achievable. If EPA wants us to remain a willing participant, their going back and changing what was already agreed upon is not how to do it.”

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John G. Smith is Newcom Media's vice-president - editorial, and the editorial director of its trucking publications -- including Today's Trucking,, and Transport Routier. The award-winning journalist has covered the trucking industry since 1995.

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