| Driver's license required in the U.S. and Canada in order to drive oversized vehicles. In general, you must be 18 to get a CDL, and many states do not allow CDL holders under 21 to drive outside the licensing state.
In written form, there is a general knowledge test specific to the class of CDL you wish to obtain (a rough breakdown is: class A is segmented vehicles like tractor-trailers, class B is straight trucks, busses, etc. weighing over 26,000 pounds GVWR, class C is anything else), then extra tests for each particular endorsement you need for the vehicle you will be driving (air brakes, passengers, hazmat, school bus). A pre-trip inspection test and road test are also necessary.
Alcohol regulations for commercial drivers are considerably stricter than for others; whether in a commercial vehicle or not, a CDL holder must have a BAC below .04 to drive; contrast this with .08-.10 for other drivers. | 
