Emissions Rulemaking Under Review – What It Means for Trucking

The Environmental Protection Agency (EPA) has taken a significant step in reviewing emissions rulemaking that could have widespread implications for the trucking industry. On Wednesday, EPA Administrator Lee Zeldin announced that the agency is reassessing the Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles – Phase 3. These regulations, initially set under the Biden-Harris administration, were to begin with model year 2027 trucks and extend through 2032.

The Cost of Compliance

One of the primary concerns with the Phase 3 regulations is the substantial cost burden they place on truck manufacturers and fleets. Opponents argue that the additional emissions reduction requirements, particularly for nitrogen oxide (NOx), could increase the cost of a new Class 8 tractor by tens of thousands of dollars.

At the recent 2025 TMC annual meeting, Mike Tunnell, Senior Director of Environmental Affairs and Research at the American Trucking Associations, noted that modern diesel trucks have already achieved a 99% reduction in NOx since 1973 and a 99% reduction in particulate matter (PM) emissions since 1987. Given these advancements, many industry leaders question the necessity of additional costly regulations.

The CARB Challenge

While the EPA’s review may signal a shift in federal policy, the trucking industry still faces challenges from state-level emissions rules, particularly those set by the California Air Resources Board (CARB). Although CARB recently withdrew its Advanced Clean Fleets rule, its Advanced Clean Trucks (ACT) rule remains in place.

Under ACT, starting with model year 2024, Class 7 and 8 truck-tractors must be at least 5% zero-emission vehicles (ZEVs), with that percentage increasing to 40% by 2032. Several states, including Massachusetts, New Jersey, New York, Oregon, and Washington, have already adopted the ACT framework, with up to 10 more states considering joining.

Regulatory Uncertainty and OEM Dilemmas

Adding another layer of complexity, the Government Accountability Office (GAO) recently determined that Congress cannot review the EPA waivers granted to California for its stricter emissions rules under the Congressional Review Act. This finding means that even if federal regulations change, California and other adopting states may still enforce their own stricter emissions requirements.

This regulatory uncertainty presents a major challenge for truck manufacturers (OEMs) and fleets. Should OEMs continue producing CARB-compliant trucks even if federal mandates are removed? Would it be more efficient to manufacture different models for different regulatory environments?

Alissa Recker, Product Regulatory Affairs Engineer at Daimler Truck North America, described this as the “most crowded and most uncertain regulatory landscape that we as OEMs have ever worked with.” With shifting federal policies, state-by-state discrepancies, and unclear legislative paths, trucking companies must stay informed and adaptable.

What’s Next?

As the EPA moves forward with its review, the trucking industry must prepare for potential shifts in emissions regulations. Fleets and carriers should closely monitor federal and state-level policy developments, advocate for practical regulations, and strategize accordingly to balance compliance costs and operational efficiency.

Stay tuned to the Freight and Fuel Newsletter for updates on how these evolving regulations will impact your business.