The regulatory tide is turning, but not in the way many expected. This article provides an overview of CARB Vehicle Emission Regulations and what this means for your fleet, compliance strategy, and your long-term planning. In 2025, the trucking industry is seeing a surprising shift: a partial rollback of some vehicle emissions mandates from the California Air Resources Board (CARB) and a softening stance from federal regulators. For fleet operators, this creates a rare window of flexibility amid years of tightening restrictions. Learn how to navigate the evolving patchwork of state and federal mandates, why this regulatory reprieve doesn’t eliminate compliance risks, and how forward-thinking fleets are using this moment to realign priorities without losing momentum on sustainability goals.

Understanding the Rules

The California Air Resources Board (CARB) is a state agency that oversees air quality standards, including transportation. CARB announced a series of new rules focused primarily on transitioning commercial fleets toward zero-emission vehicles (ZEVs). If you own, operate, or manage commercial vehicles, it’s important to learn about the regulations and understand your responsibilities under these rules. These rules establish varying vehicle specifications and/or operating requirements that apply to different vehicle and fleet types and center on four key changes from prior CARB vehicle emissions rules:

1. They apply to all vehicles operating in the state of California, regardless of domicile. Prior programs required out-of-state units to be compliant, but only domiciled units required reporting.
2. Compared to prior CARB rules, these requirements go beyond individual vehicle specifications. You still need to verify a vehicle’s specifications are California-approved, but now you also have to confirm the vehicle type meets additional requirements based on its intended use (i.e., drayage and TRU) and your broader fleet composition.
3. The regulations aim to phase out traditional internal combustion engine (ICE) vehicles and mandate transition toward ZEVs, such as battery-electric and hydrogen fuel-cell vehicles. 
4. They will be enforced using a wide range of methods, including controls at licensing and registration points, through roadside cameras and checkpoints, during CARB inspections, and at end destinations (i.e., ports).

The CARB vehicle emission rules have many requirements that can affect your business in different ways. It is imperative that you are aware of each rule and the areas of your business they may affect and understand and plan for your compliance requirements, including vehicle registration, testing, reporting, and replacement deadlines. You must also develop a compliance strategy specific to your fleet by leaning on the expertise of an industry-leading third-party provider like Ryder.

Heavy-Duty Omnibus Regulation

Starting in 2024, the CARB regulation will cut engine NOx emissions to about 75% below current standards and 90% below current standards in 2027. And, while the EPA is also mandating lower NOx engines for the rest of the country beginning in 2024, CARB’s requirements are more stringent. This will impact the types and availability of engines for most asset classes. For companies looking to buy or lease new vehicles in California, these CARB standards go into effect for all engine OEMs, with production starting January 1, 2024. Details about engines available to meet CARB standards, in some cases, are still being developed by engine OEMs. Several important aspects to know about engine options and regulation requirements are:

• The Heavy-Duty Omnibus Regulation applies to all new non-gasoline (diesel, natural gas) internal combustion engine (ICE) equipment purchases in California above 14,000 GVWR, regardless of company size or revenue.
• OEMs have announced minimal production of diesel engines that meet the new 2024 CARB standards, resulting in dramatically fewer slots. Potential alternative options for these engines will be octane (gas), ZEVs, and redeployment of existing equipment.
• Engine production and availability are limited and uncertain across multiple engine OEMs.
• 2023 production slots with 2023 engine technology and/or used vehicles sold in or into the state, with 2023 or older engines, are not affected, as this regulation applies to 2024 and newer engine model years (MY).

Advanced Clean Trucks (ACT)

The Advanced Clean Trucks (ACT) regulations mandate minimum ZEV sales in California for original equipment manufacturers (OEMs), starting in MY2024 and resulting in 100% ZEV sales in 2035. Business entities that meet select criteria must submit a one-time large entity report (LER) detailing information about their operations (i.e., number of vehicles in their fleets, including vehicle type, make, model, and engine type). In California, LERs were due April 2021. Other U.S. states have the ACT rule and also require state-specific LERs.

Advanced Clean Fleets (ACF)

CARB proposed the Advanced Clean Fleets (ACF) regulation to transition diesel to ZEV by 2045. In December 2023, CARB announced the delay of enforcement while the EPA considers the waiver. The ACF rule transition to ZEV for “high priority” fleets, which are defined as fleets with 50 or more vehicles operating in California or companies that generate more than $50 million in annual revenue and have at least one vehicle operating in California. Fleets that meet either of these criteria can transition to ZEV under two compliance schedules. The first (default) option is called the Model Year schedule and requires all new vehicles after January 1, 2024, to be ZEVs. This is a good option for fleets that do not see wide variability and are trying to maximize the useful life of their existing ICE units. The second option is called the Milestone Schedule and allows fleets that opt in to phase in ZEVs from 2025 through 2042 as a percentage of their overall fleets. The ACF requirements for drayage apply to vehicles that haul cargo containers picked up from or dropped off at a marine port or rail yard. All drayage units (ZEV and ICE) operating in California must be registered in CARB’s drayage portal. Any new units registered for drayage use must be ZEVs. Existing ICE units registered for drayage by December 31 can get legacy status at no additional cost if they meet specific requirements. To maintain legacy status, these units are required to visit a port or railyard at least once per year, among other limitations.

Transport Refrigeration Unit (TRU) Requirements

CARB vehicle emission laws also have changes to the Transport Refrigeration Unit Airborne Toxic Control Measure (TRU ATCM) compliance schedule, including
conversion to zero-emission truck TRUs. CARB’s amendments to the TRU ATCM regulation were created to further reduce emissions from diesel-powered TRUs and transition TRU trucks to zero emissions. In response, OEMs are implementing a new refrigerant for newly manufactured TRUs. MY 2023 and newer TRUs meet a more stringent emission standard. Fleet owners, including fleet operators with leased vehicles, must meet the following requirements by December 31, 2023:

• Expanded TRU reporting, operating fees, and compliance labels. Each operating fleet must register all TRUs, including trailer TRUs, with CARB. Beginning December 31, 2023, CARB will assess and collect fees from owner/operators of TRUs every three years, and owner/operators must install new compliance labels to their TRU, which CARB will provide.
• Register and keep all refrigerated equipment operating in California up-to-date in the CARB ARBER database.

Clean Truck Check (formerly, Heavy-Duty Inspection and Maintenance) Program

Why Start Compliance Now?

The journey to compliance with emission standards takes time. Starting early allows for effective planning, sourcing of vehicles, and infrastructure development and may help your company better capitalize on these financial benefits. Many governmental and nongovernmental organizations offer incentives, grants, and subsidies to support the adoption of zero-emission vehicles. Starting early, non-compliance with CARB regulations could lead to hefty fines and penalties (up to $10,000 per vehicle per day per rule). Starting early minimizes the risk of noncompliance and its associated costs. 

Navigating CARB Regulations with a Trusted Third-Party Provider

As the deadlines for these vehicle emission rules approach, commercial vehicle owners and transportation managers are facing the challenge of transitioning their fleets to comply with these regulations. Working with a trusted third-party provider like Ryder is a strategic move toward seamless compliance while reaping the benefits of expertise, resources, and industry experience. As an established leader in the commercial transportation industry, Ryder possesses in-depth knowledge of these emerging regulations, and the challenges and opportunities they present. Trusting Ryder allows you to leverage a wealth of expertise on compliance considerations, ZEV available in the marketplace, and the latest regulatory developments. We are here to help you make informed decisions, avoid potential pitfalls, and evolve your fleet to meet your company’s needs. Transitioning to ZEVs involves more than just procuring new trucks. It requires a comprehensive approach that aligns with a companies operational needs. 

Ryder specializes in providing customized fleet solutions based on individual company requirements. This includes fleet leasing and dedicated transportation solutions, as well as truck rental with vehicles that comply with CARB rules. From vehicle selection and financing options to maintenance and charging infrastructure, Ryder tailors a comprehensive plan that addresses CARB regulations while minimizing disruptions to business operations. Ryder closely monitors regulatory changes and our approach to compliance can help you stay ahead of updates and ensure that your fleet meets the latest requirements. While compliance primarily falls under the responsibilities of fleet owners and operators, collaborating with a trusted third-party provider like Ryder can simplify the process, allowing you to focus on your core operations while benefiting from industry leading expertise, tailored solutions, and a proven commitment to sustainability. As companies strive to meet CARB’s requirements, partnering with Ryder could be the key to a successful and seamless transition.