The federal government requires a special Commercial Drivers License to operate vehicles with gross vehicle weight of 10,001 or more pounds. A CDL is also required for vehicles that carry 9 or more passengers for commercial purposes. This requirement includes tow trucks, tractor-trailers and buses.
Before 1986 these regulations were left up to the states, but The Commercial Motor Vehicle Safety Act of 1986 standardized the process on a federal level. Each state has application processes and offers specialty training. Light vehicles such as pickup trucks and light vans generally do not have a Gross Vehicle Weight of 10,000 and do not require a CDL.