California Air Resources Board

For more than 50 years, the California Air Resources Board (CARB) has led in measures to reduce harmful pollution from primarily medium- and heavy-duty fleet emissions. These efforts have delivered cleaner air and improved public health by mitigating the harms posed by pollutants, while sparking innovation that benefits drivers everywhere.

Still, California suffers from some of the worst air pollution in the nation, with medium- and heavy-duty trucks contributing a significant share of harmful emissions. Despite progress in reducing pollution from various sectors, five of the 10 most polluted cities in the U.S. are in California, and two air basins in California, South Coast and San Joaquin Valley, are designated as in “extreme nonattainment” for ozone. This means about half of all Californians live in areas with air that is dangerously polluted. These conditions pose serious public health risks, especially for communities already burdened by higher rates of asthma, heart disease, and lung conditions, which contribute to shorter life expectancy. Meanwhile, climate change is increasing wildfires, drought, floods, heat events, and the ease with which ozone and particulate matter form in California. Hence, more work is needed to reduce emissions in California.

A New Phase of Fleet Regulations

CARB staff has begun a new phase of work to reduce criteria air pollutant, greenhouse gas, and toxic emissions consistent with State and federal law that includes primarily medium- and heavy-duty fleet emissions. Please visit the Meetings & Workshops page for upcoming events.

Why Action Now Matters

Reducing emissions from the transportation sector is central to CARB’s mission to protect public health and improve air quality across California. Vehicle emissions remain a significant contributor to statewide pollution, and medium- and heavy-duty fleets generate a disproportionate share of those impacts. Communities already burdened by elevated pollution levels and climate-related stressors are likely to continue experiencing disproportionate harms if current conditions persist. Advancing cleaner transportation technologies furthers CARB’s mission by supporting healthier air, reducing pollution burdens, and strengthening California’s resilience to floods, wildfires, drought, and extreme heat.  

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