In the United States, commercial vehicle drivers operating heavy, large, or hazardous materials vehicles in commerce must have a commercial driver’s license (CDL). A CDL is required to drive any bus, tank truck, or vehicle carrying passengers.

To obtain a license, the operator must first pass a specialized knowledge examination and perform a comprehensive driving road test. School bus drivers must also pass a background check.

Before October 1986, commercial drivers in most states can operate a large commercial vehicle using only a state-issued automobile driver’s license without proper training required. That year, Congress passed the Commercial Motor Vehicle Safety Act making it mandatory for every commercial vehicle driver to acquire a CDL.