The trucking industry in California is regulated by the following agencies:

For air emissions regulations, contact the Air Resources Board (ARB).  The ARB contact information is on this Caltrans web page:  http://www.dot.ca.gov/hq/traffops/trucks/ops-guide/air.html. 

For drivers license or vehicle registration, contact the Department of Motor Vehicles (DMV). http://www.dmv.ca.gov

For inspections, highway safety and laws, contact the California Highway Patrol (CHP) at (916)843-3400. http://www.chp.ca.gov/

For licensing of household goods carriers and tour buses, contact the California Public Utilities Commission at (800) 877-8867. http://www.cpuc.ca.gov/

For fuel taxes contact the California Board of Equalization at (916) 322-9669. http://www.boe.ca.gov/

For hauling animals, crops and produce, contact the California Department of Food & Agriculture at (916) 654-0466. http://www.cdfa.ca.gov

The California Department of Transportation (Caltrans) Office of Truck Services web page at http://www.dot.ca.gov/hq/traffops/trucks/ is the portal to

1. Truck Operations
2. Oversize/Overweight Permits http://www.dot.ca.gov/hq/traffops/permits (916) 322-1297
   
3. Legal Truck Size & Weight
4. Legal Truck Size & Weight -- Exemptions
5. Truck Routes
6. 45' Buses & Motorhomes
7. Weigh Stations/Enforcement Facilities
8. Weigh-in-Motion

Traffic Operations web link: http://www.dot.ca.gov/hq/traffops