A Class A CDL is for combinations with a GCWR of 26,001 pounds or more where the towed unit is over 10,000 pounds. Class B is for a single vehicle with a GVWR of 26,001 pounds or more. Class C covers smaller vehicles that carry hazardous materials in placarded amounts or 16 or more passengers.
Endorsements add permission for tankers, doubles and triples, hazardous materials and passengers. A CDL driver must hold a valid medical examiner’s certificate, usually through a DOT physical.
Regulation: 49 CFR 383.