The United States Department of Transportation requires commercial truck drivers to have a state-issued Commercial Driver's License and a medical examination at least every 24 months. State CDL requirements vary.
Most state CDL programs require potential commercial drivers to take a written knowledge test, which qualifies them for a learner's permit. Once a new commercial driver has his permit, he can drive with another CDL holder. This allows the learner to practice his skills and learn how to apply them in real road situations. After the permit period, the driver must take a road test to get the full CDL.
The medical examination is important to make sure a commercial driver is not suffering from any illnesses or issues that may make driving unsafe. Examples include vision problems, hearing loss and epilepsy. Diabetes can also affect a commercial driver's eligibility, although drivers suffering from it can get an exemption if they show it is adequately controlled with insulin. Missing limbs may also require an exemption, which can be obtained by showing that the driver can safely control the vehicle.
Some types of hauling require special courses and tests. Commercial drivers dealing with hazardous materials, commonly known as HazMat, are one of the most common types. Commercial drivers are also subject to background checks and must have clean driving records as well as submitting to drug and alcohol testing.