A CDL license, also known as a commercial driver's license, is required to drive large trucks and various other types of commercial vehicles legally. There are several different types of CDLs and several different classes for multiple commercial vehicles.
CDLs were originally a creation of the Commercial Motor Vehicle Safety Act of 1986 as a way to make America's roads safer by ensuring that drivers know how to operate commercial vehicles properly. The U.S. Department of Transportation requires drivers to pass a written exam, a physical examination, a drug screening and a skills test. Common commercial vehicles include tractor trailers, school buses and transit buses.