California Air Resources Board
"CARB's mission is to promote and protect public health, welfare, and ecological resources through effective reduction of air pollutants while recognizing and considering effects on the economy. CARB is the lead agency for climate change programs and oversees all air pollution control efforts in California to attain and maintain health-based air quality standards."
Each year CARB will issue or revise regulations regarding Heavy-Duty Diesel Vehicles, among other things. They publish information, resources, updates, etc on their site https://ww2.arb.ca.gov/
How does this affect me?
Whether you're buying within California or sourcing a machine from California, CARB regulations may effect you. To view/download a current copy use this link.