CARB States: A guide to understanding emissions regulations in the U.S. [2025]

The fact that diesel semi-trucks account for 18% of all U.S. vehicle emissions is a major driver behind the growing movement of states adopting the California Air Resources Board (CARB) environmental standards, collectively known as CARB states. 

In CARB states, fleets must adhere to strict emissions requirements, which often necessitates investments in newer, cleaner vehicles, or the adoption of alternative fuels. This can include transitioning to electric vehicles (EVs) or vehicles that use other low-emission technologies. 

But what exactly are these strict regulations and which states have adopted CARB policies?

What is CARB?

CARB stands for the California Air Resources Board. It's a state agency tasked with protecting public health and the environment by regulating air pollution. Being CARB-compliant means adhering to the emissions standards set by this board, which are often stricter than federal regulations. These standards aim to reduce pollutants from various sources, with a significant focus on vehicles.

For fleets operating in CARB states, compliance often involves transitioning to cleaner vehicles, such as electric vehicles, and employing telematics software to track vehicle data. CARB regulations can necessitate investments in new technologies, adjustments to maintenance schedules and careful route planning to minimize emissions. 

The requirements vary depending on the type and size of the fleet, but generally involve meeting specific emissions targets and reporting data to ensure compliance.

EPA vs. CARB: What’s the difference?

The EPA and CARB both regulate air pollution but operate at different levels. The Environmental Protection Agency (EPA) is a federal agency that sets national standards for air quality and vehicle emissions that must be met by all vehicles in the U.S. 

In contrast, the California Air Resources Board is a state agency that establishes its own, often stricter, emissions regulations. This has led to several other states choosing to adopt CARB regulations on top of existing federally mandated EPA policies.

CARB-compliant states

CARB-compliant states are those that have adopted California's stringent vehicle emissions standards, aiming to reduce air pollution and greenhouse gas emissions. These states recognize the importance of cleaner vehicles for public health and environmental protection.

Current CARB states:

• California
• Colorado
• Connecticut
• Delaware
• District of Columbia
• Maine
• Maryland
• Massachusetts
• Minnesota
• Nevada
• New Jersey
• New Mexico
• New York
• Oregon
• Rhode Island
• Vermont
• Virginia
• Washington

While most states are moving toward stricter emissions regulations, some states have repealed previous CARB adoption. 

Repealed CARB states:

• Arizona
• Florida

Fleet CARB regulations examples

CARB regulations significantly impact fleet operations, pushing for cleaner vehicle technologies and reduced emissions. Here are some key regulations fleets operating in CARB states should be aware of:

• Advanced Clean Trucks (ACT) Rule: This rule mandates manufacturers to increase the production and sales of zero-emission trucks, gradually shifting the market towards cleaner heavy-duty vehicles.
• Advanced Clean Fleets (ACF) Rule: The ACF rule requires fleets, especially large ones, to transition to zero-emission vehicles for their operations, setting specific timelines and targets for this transition.
• Truck and Bus Regulations: These regulations focus on reducing emissions from existing heavy-duty diesel trucks and buses, often through engine upgrades, retrofits or the replacement of older vehicles.
• Zero-Emission Vehicle (ZEV) Requirements: These requirements set specific percentages of zero-emission vehicles that must be included in a fleet's overall makeup, accelerating the adoption of electric and other clean technologies.

It's important to note that specific regulation requirements can vary by state, and the CARB states chart below indicates which regulations apply in each location.

Compliance strategies for CARB-state fleets

Navigating CARB compliance can be complex for EV fleet managers. Proactive strategies are essential to stay up to date on regulations and minimize operational disruptions. This involves everything from regular audits and strategic planning to leveraging financial incentives and investing in alternative fuel infrastructure. 

Here are some key compliance strategies for fleets operating in CARB states.

1. Conduct regular fleet audits 

Regular fleet audits are crucial for assessing current emissions levels and identifying areas for improvement. This involves evaluating the age and condition of vehicles, analyzing fuel consumption and monitoring maintenance records. 

Audits help fleet managers understand their compliance status and pinpoint necessary adjustments to meet CARB standards. In addition, utilizing telematics devices and fleet management software helps streamline the process by easily comparing your current fleet data to zero emissions goals. 

2. Develop a clear CARB-compliance timeline 

Creating a detailed compliance timeline is essential for a smooth transition. This timeline should outline key milestones and reporting deadlines. More specifically, it's a good idea to break down the timeline into actionable phases, including research and evaluation of ZEV options, procurement of new vehicles, infrastructure installation and staff training.

A clear timeline allows fleet managers to plan their investments and operations effectively, ensuring they meet CARB requirements without last-minute scrambling.

3. Utilize available incentives and grants  

CARB states often offer incentives and grants to support fleets in their transition to cleaner technologies. For example, California’s HVIP (Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project) provides vouchers to reduce the upfront cost of purchasing hybrid and zero-emission trucks and buses to combat smog. 

But beyond California’s HVIP, several different incentives and federal programs may apply. Leveraging these grants can significantly reduce the financial burden of compliance and help you weigh the long-term benefits of minimizing emissions.

4. Invest in alternative fuel infrastructure

Transitioning to alternative fuels, such as electricity or hydrogen, requires careful planning and infrastructure investment. This means thoroughly evaluating each fuel's benefits prior to installing charging or refueling stations.

Strategic investment in infrastructure ensures that fleets can efficiently operate their alternative fuel vehicles and meet CARB’s emission requirements.

5. Train drivers and fleet managers

Proper training is essential for the successful implementation of CARB compliance strategies. Drivers and fleet managers need to understand the new regulations, operate alternative fuel vehicles efficiently and adopt best practices for emissions reduction. 

Training programs should cover topics such as vehicle maintenance, fuel efficiency and compliance reporting.

Trust Geotab to bring your fleet to the future

As environmental concerns escalate, more and more states are adopting the emissions standards pioneered by CARB, making it crucial for fleets nationwide — and even worldwide — to prepare for these changes.

Beyond simply complying with CARB states' requirements, embracing cleaner technologies and practices is becoming essential for long-term operational viability and environmental responsibility. 

Geotab's fleet management software empowers fleets to monitor and manage emissions, optimize fuel consumption and track vehicle performance, all critical aspects of CARB-compliance solutions. In fact, Geotab is the only provider with both a CARB Clean Truck Check Certification and T-harness installation exemption, ensuring seamless compliance with the Heavy-Duty Vehicle Inspection and Maintenance (HD I/M) Regulation.