CARB holds public workshop on Advanced Clean Cars II Amendments

27 June 2024

The California Air Resources Board (CARB) held a public workshop on June 26^th, discussing potential amendments to the Advanced Clean Cars II (ACC II) regulation that was adopted in August 2022.

The ACC II rule includes two key components: the LEV IV emission standards for criteria air pollutants and the zero-emission vehicle (ZEV) program, which mandates 100% new ZEV sales (including up to 20% PHEVs) in California from 2035. CARB is now proposing several amendments to the ACC II package to better align California requirements with the federal Tier 4 emission standards and MY 2027-2032 GHG emission standards that the Environmental Protection Agency (EPA) finalized in March 2024.

Criteria Air Pollutants. The key issues and proposed changes related to the LEV IV regulation include:

• Light-Duty Vehicles
  • NMOG+NOx fleet average standard—LEV IV maintains the NMOG+NOx fleet average at 30 mg/mi, excluding ZEVs from 2029, while EPA’s Tier 4 standards lower NMOG+NOx fleet average to 15 mg/mi from 2032 while continuing to include ZEVs in the average. No changes are proposed, as CARB believes both standards require similar levels of emission control.
  • NMOG+NOx Certification Bins—CARB will not amend the LEV IV bin structure for light-duty vehicles to fully harmonize with Tier 4. However, CARB proposes to eliminate the “Cleaner Car” provision that currently prohibits manufacturers from certifying vehicles in California at a higher emission bin than they certify to with the EPA. This change will provide manufacturers with greater flexibility in certifying to the new EPA Tier 4 bins that do not exist under CARB LEV IV.
  • PM Emission Standard. CARB proposes to lower the LEV IV PM standard from the current 1-3 mg/mi to 0.5 mg/mi from 2030 to better align with the EPA rulemaking.
• Medium-Duty (Class 2b and Class 3) Vehicles
  • NMOG+NOx fleet average standard—LEV IV includes an NMOG+NOx fleet average standard for Class 2b of 150 mg/mi and for Class 3 of 175 mg/mi by 2030 (excluding ZEVs from averaging), while the Tier 4 standard is 75 mg/mi for all MDVs by 2033 (including ZEVs in the average). CARB proposes to further reduce MDV ACC II NMOG+NOx fleet average standards to 130 mg/mi by 2032 to achieve equivalent stringency to the EPA Tier 4 standard.
  • NMOG+NOx Certification Bins—CARB proposes to remove MDV NMOG+NOx bins higher than 170. This would harmonize MDV bins in the 75-170 mg/mi range with the respective Tier 4 bins (however, Tier 4 also includes bins below 75 mg/mi).
  • PM Emission Standard. CARB proposes to lower the LEV IV MDV PM standards of 8-10 mg/mi (FTP) and 5-8 mg/mi (US06) to 0.5 mg/mi (FTP and US06) from 2031 to better align with Tier 4 and achieve further PM emission reductions.
  • Other Changes—Changes are proposed to the US06 and moving average window (MAW) testing requirements for MDVs as well as to evaporative emission testing.

GHG Emissions. While the ACC II regulation does not include fleet average GHG emission standards, the ACC II ZEV program is likely to provide greater emission reductions for the California vehicle fleet than the EPA 2027+ GHG regulation, according to CARB analysis. Even though California seems to be on track to meet the overall emission target, CARB is concerned with the risk of “backsliding”, where conversion of smaller size vehicles to ZEV platforms could result in increased CO₂ emissions from internal combustion engine (ICE) models.

To prevent “backsliding”, CARB will propose an ICE-only fleet average GHG emission standard (ICEs + PHEVs) beginning in the 2030 model year. The numerical value of the standard has not yet been proposed.

One of the issues discussed at length at the workshop were emissions from plug-in hybrids, which are allowed under the ACC II regulation as the only type of ICE vehicle past 2035. CARB presented real-world data, which suggests that the existing certification values overstate the GHG emission benefits of PHEVs. To address the issue, the agency proposes that for PHEVs, the ICE-only fleet average GHG standard be based solely on gasoline operation. The current Fleet Utility Factor method, where the electric share of the vehicle mileage traveled (eVMT) is calculated based on the PHEV all-electric range will no longer be used. CARB is seeking input on the future PHEV charge-sustaining emission rates and appropriate stringency of the standard.

Other proposed changes related to ACC II GHG provisions include the expiry of ACC I emission credits after MY 2029 and a gradual phase-out of off-cycle credits such as those related to vehicle air conditioning systems.

Finally, CARB intends to adopt the EPA’s updated medium-duty passenger vehicle (MDPV) definition for the 2030 and subsequent model years, maintaining the current definition through the 2029 model year. The updated definition would be used for the purpose of both criteria pollutant and GHG emission regulations.

The workshop also discussed ZEV assurance measures, including consumer-facing EV labels, interoperability of EV charging, and ACC II battery label requirements.

CARB expects to finalize the ACC II amendments at a Board meeting in late Spring or early Summer 2025. The agency will accept public comments on topics discussed at the workshop by July 26, 2024. Approved comments can be viewed on the ACC II workshop comments log webpage.

Source: CARB