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Welcome to ZEV Help! Your Guide to Zero-Emission Commercial Vehicles

ZEV Truck Regulation Tracker 2026

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  • ZEV Truck Regulation Tracker 2026

Zero-emission truck rules changed more in 2025 than in the previous five years combined. This tracker summarizes where the major federal and California regulations for medium- and heavy-duty trucks stand, and what it means for fleets.

Status as of October 2026. These rules are actively litigated and can change quickly. ZEV Help is a reference resource, not legal advice. Confirm current requirements with EPA, CARB, or your state agency before making compliance or purchasing decisions.

At a glance

RuleAgencyWhat it requiredCurrent status
Advanced Clean Trucks (ACT)CARBManufacturers sell a rising share of zero-emission trucks in California.Waiver revoked Congress overturned the federal waiver in June 2025. California is challenging that in court.
Advanced Clean Fleets (ACF)CARBFleets phase zero-emission trucks into their operations.Mostly withdrawn CARB withdrew its waiver request in January 2025. The state and local government fleet requirements remain.
Omnibus Low NOxCARBMuch tighter NOx limits and longer warranties for new diesel engines.Waiver revoked Overturned by Congress in June 2025 and under litigation.
GHG Phase 3EPAStricter CO₂ standards for model year 2027–2032 trucks.Rescinded EPA finalized rescission of the vehicle greenhouse gas standards and the 2009 endangerment finding in February 2026. Faces legal challenges.
2027 Heavy-Duty NOx ruleEPALower NOx limits for model year 2027 engines.Under reconsideration EPA announced it would reconsider the rule in 2025. Check for revised compliance dates.
Clean Truck PartnershipCARB + truck makersManufacturers agreed to follow California standards in exchange for lead time.Disputed After the waivers were revoked, manufacturers and CARB went to court over whether the agreement still binds.

What happened in 2025

January: CARB pulls back on Advanced Clean Fleets

Ahead of the change in federal administration, CARB withdrew its request for the EPA waiver needed to enforce ACF on private high-priority and drayage fleets. The requirements for state and local government fleets, which do not need a waiver, stayed in place. Read our coverage.

June: Congress overturns California’s truck waivers

Congress used the Congressional Review Act to nullify the EPA waivers for Advanced Clean Trucks, Omnibus Low NOx, and Advanced Clean Cars II, and the President signed the resolutions in June 2025. California sued, arguing waivers are not rules subject to the Act. Until the courts decide, manufacturers are not treating ACT sales mandates as enforceable.

August 2025 to February 2026: EPA rescinds greenhouse gas standards

EPA proposed rescinding its 2009 endangerment finding and the vehicle greenhouse gas standards that rest on it, including the heavy-duty Phase 3 standards, in August 2025, and finalized the rescission in February 2026. Legal challenges are expected to run for years.

What about other states?

Several states adopted California’s Advanced Clean Trucks rule, including Oregon, Washington, New York, New Jersey, Massachusetts, and Vermont. Because those states relied on California’s waiver, the 2025 congressional action affects them too, and several have delayed or paused enforcement. If you operate in one of these states, check your state environmental agency for its current position.

What this means for fleets

  • Mandates have softened, but the market hasn’t disappeared. Customer sustainability goals, port and local rules, and fuel savings on the right routes still drive purchases.
  • Government fleets in California remain subject to ACF purchase requirements.
  • Diesel engine planning is in flux. With the 2027 NOx rule under reconsideration, watch for pricing and pre-buy decisions from your truck dealer.
  • Incentives changed too. See our 2026 incentives guide for what’s still available.
Explainers on these rules
Related news and commentary
Official sources

Last reviewed: October 2026