California Air Resource Board developed the Clean Air Act which tackles California's mobile source pollution. Heavy-duty diesel vehicles over 14,000 pounds are major polluters. Despite CARB's past efforts, these vehicles still contribute most of California's on-road NOx and PM 2.5 emissions.

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Modern heavy-duty diesel trucks have emission control systems, but malfunctions can hinder air quality goals. The Clean Truck Check ensures timely maintenance and repairs for these vehicles, promoting fairness among operators.

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It combines roadside emissions checks, improved testing with onboard diagnostics, regular emissions inspections, and compliance for freight contractors, seaports, and railyards. This regulation is one of CARB's most impactful, projected to cut over 81 tons of NOx and 0.7 tons of PM emissions daily by 2037, saving 7,500 lives.