Over the past year, PMTA has closely monitored the evolving landscape surrounding California's Low NOx Omnibus Rule and related federal emissions regulations. Since our last update, several significant developments have reshaped the regulatory outlook for Pennsylvania motor carriers—and they represent meaningful progress for the trucking industry.

Federal Action Blocks California's Rule

In June 2025, the Trump Administration signed legislation overturning California's federal waiver that allowed the state to impose its Advanced Clean Trucks (ACT) and Low NOx emissions requirements on other states.

For Pennsylvania, this means the Commonwealth is no longer subject to California's Low NOx Omnibus standards simply because it previously adopted the rule. The federal action effectively prevents California's emissions mandates from being enforced beyond its borders under the former waiver authority.

PMTA welcomed this action, which restores greater regulatory consistency for truck manufacturers, dealers, and fleets operating across multiple states.

Pennsylvania Moves to Rescind the Rule

Building on the federal action, in 2026 the Shapiro Administration has begun the formal regulatory process to permanently rescind Pennsylvania's Heavy-Duty Diesel Emissions Control Program, which incorporated California's Low NOx standards into state regulations.

If finalized, the action would remove the regulation from Pennsylvania's books entirely, providing long-term certainty for motor carriers, equipment dealers, and truck manufacturers.

PMTA strongly supports this effort and appreciates the Administration's willingness to reconsider a regulation that raised significant concerns regarding equipment availability, increased vehicle costs, and implementation challenges.

EPA Proposes Major Changes to the Federal Low NOx Rule

At the federal level, in July the U.S. Environmental Protection Agency (EPA) proposed substantial revisions to its own 2027 Heavy-Duty Low NOx standards.

Among the most significant proposed changes are:

• Maintaining the current 5-year/100,000-mile emissions warranty instead of expanding it to 10 years/450,000 miles.
• Delaying the more stringent useful-life requirements for heavy-duty engines until 2030.
• Providing manufacturers with greater flexibility during the transition to the new standards.
• Allowing certain non-compliant engines to be sold through a nonconformance penalty program.
• Eliminating mandatory diesel exhaust fluid (DEF) speed and power derates for new trucks and replacing them with dashboard warning notifications.

According to EPA, these proposed revisions could reduce the cost of a new heavy-duty truck by as much as $6,000 and save the trucking industry approximately $12 billion if adopted as proposed.

It is important to note that these changes are currently proposals, not final regulations. EPA will accept public comments through August 29, 2026, before issuing a final rule.

What This Means for Pennsylvania Carriers

Taken together, these developments represent significant progress toward a more practical and balanced regulatory framework for Pennsylvania's trucking industry.

While work remains at both the state and federal levels, the overall direction is encouraging. The federal government has acted to prevent California's emissions mandates from expanding into other states, Pennsylvania is moving to eliminate its own CARB-based regulation, and EPA is proposing revisions that recognize many of the operational and economic concerns raised by the trucking industry.

PMTA will continue participating in the state and federal rulemaking process alongside the American Trucking Associations and other industry partners to ensure the trucking industry's voice is heard as these proposed changes are considered.

As always, we will keep members informed as these proposals move toward final action and continue advocating for emissions policies that are technologically achievable, economically responsible, and supportive of a safe, modern trucking industry.