The Federal Motor Carrier Safety Administration's commercial driver's license (CDL) program standardizes the requirements America's truck drivers must meet to drive certain trucks and trailers. CDL classes range from A to C, with the weight of the truck and nature of its cargo determining the class required to drive it, and certain specialized vehicles and cargo types require additional endorsements to the license. Drivers take the CDL skills test in the same type of vehicle that the CDL class or endorsement will allow them to operate.

Auto Transport

Auto transports carry inventory to dealerships, and their drivers must have a Class A CDL. Transport drivers need to be skilled enough to execute multiple-point turns on local roads in the vehicle, as many of their destinations will be in heavily trafficked areas. Logistics employers also expect their drivers to know how to properly secure the vehicles they haul and to be able to fasten tarps and covers over the cargo when driving conditions demand it.

Flatbeds

Flatbed drivers must hold either a Class A or B CDL depending on the cargoes they carry, and drivers who haul hazardous materials must also get the "H" endorsement. Drivers need to know how to properly secure their cargo to prevent it from shifting or becoming dislodged. Flatbed truckers who haul oversized loads also have to get the required permits for the route they travel and install all required banners, lights and reflectors. Drivers also need to know the procedures for loading their cargo and be able to recognize balanced and unbalanced loads.

Tankers

Tanker drivers must have an "N" endorsement to drive a tanker and an "H" endorsement if they haul fuel, liquefied gas or any other hazardous materials. Tanker drivers must demonstrate that they're able to inspect their vehicles, detect leaks and know how much empty space to leave in the tank to accommodate expanding liquid. Tankers are particularly challenging vehicles to drive because their liquid cargoes tend to slosh in the tank, forcing the driver to compensate for the weight distribution, and the truck's high center of gravity makes it top-heavy and more susceptible to rollover accidents than other commercial vehicles.

Tractor-Trailers

Drivers must have a Class A CDL for cabs and trailers with a gross combination weight rating of more than 26,000 lbs., while a Class B covers cabs that tow trailers weighing 10,000 lbs. or less. If a driver either doesn't take or fails her air brake skills test, the state will issue her a restricted CDL that prohibits her from driving a tractor-trailer equipped with air brakes. Drivers who haul two or three trailers with a single cab need to get the "T" endorsement and must demonstrate that they're proficient enough to handle the difficult trailer configuration without causing their trailers to fishtail.