In the United States of America, the Commercial Driver's License. This, as opposed to a normal driver's license, is required for U.S. drivers of trucks, buses, limousines, and all vehicles hauling hazardous materials.
There are three classes of Commercial Driver's License; A, B, and C, by type of vehicle.
CLASS A: Any Tractor/Trailer combination that has an actual weight, declared weight or GVWR
of 26,001 LBS. or more, provided towed vehicle is more than 10,000 LBS.
CLASS B: Any single motor vehicle that has an actual weight, declared weight or GVWR of 26,001 LBS. or more, or any such vehicle towing a vehicle of 10,000 LBS. or less.
CLASS C: Any motor vehicle that has an actual weight, declared weight or GVWR of less than 26,001 LBS. when endorsements "H" or "P" would be required on the driver license OR any combination of motor vehicles where the towing vehicle is less than 26,001 LBS. GVWR and the towed vehicle has a GVWR of 10,000 LBS. or less, but together they weigh 26,001 LBS. or more.
In addition, there are endorsements for transport of hazardous materials, driving tank vehicles with a capacity greater than 1,000 gallons, vehicles designed to carry 16 or more passengers, tank vehicles hauling hazardous materials, farm vehicles, and emergency vehicles.
Getting a CDL requires special written and road tests, and is required for some jobs such as driving delivery trucks and transit vehicles.