ATCM 93120 Phase 2 is California's emission standard for new heavy-duty vehicles

ATCM 93120 Phase 2 refers to California's Advanced Technology Clean Trucks regulation, which sets stricter emission limits for new heavy-duty vehicles sold in the state starting in 2027. If you own or operate trucks, buses, or other heavy vehicles in California, this standard affects which models you can register and what you may need to do when your current vehicle reaches the end of its useful life.

The regulation does not change how you renew your registration for vehicles you already own. It does affect what new vehicles are available for purchase and what you can legally register as a replacement when you need one. Understanding the timeline and what vehicles meet the standard helps you plan ahead if you operate a fleet or rely on heavy-duty vehicles for work.

Key Takeaways

  • ATCM 93120 Phase 2 applies to new heavy-duty vehicles registered in California starting January 1, 2027, not to vehicles already on the road.
  • The regulation requires manufacturers to reduce nitrogen oxide (NOx) emissions by roughly 90 percent compared to current standards.
  • Vehicles that do not meet Phase 2 standards cannot be registered as new in California after the effective date, though used vehicles and out-of-state registrations are not affected.
  • If you operate heavy trucks or buses in California, you should check with manufacturers now about which 2027 and later models will meet the standard.
  • Your current vehicle registration does not change, but you may face limited options when you need to replace an aging vehicle.

When Phase 2 takes effect and what vehicles it covers

Phase 2 becomes mandatory on January 1, 2027. Starting that date, any new heavy-duty vehicle — including Class 7 and Class 8 trucks, transit buses, and school buses — sold and registered in California must meet the NOx emission limits set by the regulation. Manufacturers cannot register a new vehicle that fails to meet these standards in the state after that date.

The regulation applies only to new vehicles. If you own a truck or bus registered before 2027, you can continue to renew its registration normally. Used vehicles, even if they are newer models, can be registered in California without meeting Phase 2 standards. Vehicles registered outside California and operated temporarily in the state are also not subject to the rule.

Heavy-duty vehicles include Class 7 and Class 8 trucks (those with a gross vehicle weight rating above 26,000 pounds), transit buses, school buses, and some medium-duty vehicles depending on their configuration. Light-duty trucks and passenger vehicles are not covered by this regulation.

What the emission limits actually require

Phase 2 requires manufacturers to reduce nitrogen oxide (NOx) emissions to approximately 0.02 grams per brake horsepower-hour for most heavy-duty engines. This represents roughly a 90 percent reduction from the current Phase 1 standard of 0.20 grams per brake horsepower-hour. The tighter limit forces manufacturers to use advanced emission control technology, including selective catalytic reduction (SCR) systems and other post-combustion treatments.

Manufacturers have known about this requirement since the regulation was adopted, and most major truck and bus makers have already begun developing or testing compliant engines. Some models may already be available that meet Phase 2 limits, even though the mandate does not take effect until 2027. You can ask dealers or manufacturers directly whether specific 2027 or 2028 models will carry Phase 2-compliant engines.

How this affects your vehicle registration renewal

If you currently own a heavy-duty vehicle registered in California, Phase 2 does not change your registration renewal process. You renew your registration the same way you do now, through the California Department of Motor Vehicles (DMV), and your registration remains valid as long as your vehicle passes smog checks (if required) and you pay your renewal fees.

The regulation only prevents new vehicles that do not meet the standard from being registered for the first time in California. It does not force you to replace or retrofit existing vehicles. However, if your current vehicle reaches the end of its useful life and you need to purchase a replacement, your options for new vehicles will be limited to those that meet Phase 2 standards.

Planning ahead if you operate heavy trucks or buses

If you operate a fleet or depend on heavy-duty vehicles for your business, now is the time to contact manufacturers and dealers about Phase 2 compliance. Ask which 2027 and later models will meet the standard and what the cost difference is compared to current models. Some manufacturers may offer Phase 2-compliant versions earlier than required, while others may wait until 2027.

If you plan to replace a vehicle between now and 2027, you can still register a new vehicle that meets current Phase 1 standards. After January 1, 2027, you will need to choose from Phase 2-compliant models only. Purchasing a replacement before the important date is an option if you want to avoid the transition, though this should be weighed against the cost and your actual vehicle needs.

Used vehicle markets may also shift as Phase 2 approaches. Older heavy-duty vehicles may become more valuable as operators seek to avoid the cost of new compliant models, while Phase 2-compliant used vehicles may become available at lower prices as fleets upgrade. Monitoring these trends can help you time a purchase or replacement decision.

What happens if a manufacturer sells a non-compliant vehicle in California

Manufacturers that sell new heavy-duty vehicles in California after January 1, 2027 that do not meet Phase 2 standards face significant penalties from the California Air Resources Board (CARB). These penalties are imposed on the manufacturer, not on the buyer or owner. The DMV will not register a new vehicle that the manufacturer has not certified as Phase 2-compliant.

If you purchase a new heavy-duty vehicle after 2027, the dealer and manufacturer are responsible for ensuring it meets the standard before sale. You should not encounter a situation where you buy a new vehicle and cannot register it due to Phase 2 non-compliance, because the vehicle should not be offered for sale in California in the first place.

Frequently Asked Questions

Do I have to replace my current heavy-duty vehicle to comply with Phase 2?

No. Phase 2 applies only to new vehicles registered after January 1, 2027. Your current vehicle can continue to be registered and operated in California as long as it passes required smog checks and you pay your renewal fees. You are not required to replace it.

Can I register a used heavy-duty vehicle that does not meet Phase 2 standards after 2027?

Yes. Phase 2 applies only to new vehicle registrations. Used vehicles, even if they are newer models, can be registered in California without meeting Phase 2 standards. You can buy and register a used truck or bus that was manufactured before 2027 at any time.

What if I buy a new heavy-duty vehicle in another state and bring it to California?

If you register the vehicle in another state first, you can operate it in California temporarily. However, if you want to register it in California, it must meet Phase 2 standards if it is a new vehicle registered after January 1, 2027. Out-of-state registrations are not subject to California's ATCM 93120 requirement.

Are light-duty trucks and vans covered by Phase 2?

No. ATCM 93120 Phase 2 applies only to heavy-duty vehicles with a gross vehicle weight rating above 26,000 pounds, including Class 7 and Class 8 trucks, transit buses, and school buses. Light-duty pickup trucks and commercial vans are not covered.

Where can I find which 2027 models will meet Phase 2 standards?

Contact truck and bus manufacturers directly, or ask a dealer who sells heavy-duty vehicles in California. Manufacturers are required to certify their engines and powertrains with the California Air Resources Board (CARB) before sale. CARB's website also publishes lists of certified heavy-duty engines, though the most current information often comes directly from the manufacturer.