Regulatory Update: California Withdraws ACF Enforcement

In recent years, several states, most notably California, have worked to introduce stringent emissions regulations in an effort to reduce air pollution. Among those efforts is the California Air Resources Board’s (CARB) Advanced Clean Fleet (ACF) Regulation which is designed to gradually phase-in the use of zero-emission vehicles (ZEVs).

The proposed ACF regulations would require large commercial fleet operators, those with 50 or more vehicles over 8,500 lbs. GVW that operate in the state of California, to comply with rigorous reporting standards and/or meet the minimum requirements for the use of zero-emission vehicles.

However, as of January 14, 2025, CARB has formally withdrawn its request with the Environmental Protection Agency (EPA) to enforce the proposed ACF regulations. As a result, commercial fleet operators are no longer required to report on their vehicle inventory or meet minimum requirements for the use of ZEVs at this time.

In a communication to key stakeholders, CARB noted that is has officially withdrawn its request for authorization to add ACF regulations to its emissions program. At this time, CARB does not intend to enforce the portions of the regulations that would require federal authorization including the parts of the ACF regulations that would apply to commercial fleet operators.

That being said, it is also important to note that not all facets of the proposed ACF regulations require federal approval. The segment of the rule pertaining to state and local government remains unaffected. CARB is currently re-evaluating potential next steps but the organization remains committed to reducing air pollution to protect public health.

While this is welcome news for many fleet operators who faced the challenge of complying with potentially cumbersome reporting and vehicle standards, there are still a number of factors fleet operators need to be aware of moving forward.

Advanced Clean Truck Rule

Although ACF has been withdrawn for now, CARB was still able to gain EPA approval in 2023 for the Advanced Clean Truck (ACT) rule. This rule applies to OEMs who build vehicles over the 8,500 lbs. GVW and requires that seven percent of new vehicles sales in California to be ZEVs as of January 1, 2025. With that in mind, many OEMs are likely to require fleet operators to purchase a ZEV unit before they allocate any internal combustion engine (ICE) vehicles. This is especially true for the medium- and heavy-duty diesel chassis market.

Low NOx Omnibus ruling

In December of 2024, the EPA granted approval for California to move forward with its low NOx Omnibus ruling. This rule finalized the ability to lower current diesel engine nitrogen oxide (NOx) levels from the 2010 standard of 200 grams (.2) to 50 grams (.05). These engines are commonly referred to as CARB ’24 engines.

Currently, not all engines produced by several OEMs are CARB ’24 compliant. Therefore, it has created a backlog of orders for gasoline and diesel units to be delivered to California to ensure compliance.

Stay Informed on the Latest Regulatory Developments

While CARB withdrawing its ACF waiver request is a significant development that will certainly impact fleet operators in that region, regulatory requirements continue to evolve rapidly. It is important to stay well-informed of the latest regulations and industry standards to ensure compliance to avoid unnecessary fines or costly downtime.

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