Which document must a CDL holder carry at all times while operating a commercial vehicle?

A Commercial Driver's License (CDL) is the primary document required for operating a commercial vehicle. It serves as proof that the driver has met all necessary qualifications and undergone the appropriate training to operate specific types of commercial vehicles safely. Carrying the CDL ensures compliance with legal regulations and helps law enforcement verify the driver's credentials on the road.

While insurance documentation and vehicle registration are also important and often required by law, they are not mandatory to be carried directly by the driver in the same way the CDL is. The driver's permit is usually a learner's document and does not grant the privileges that a full commercial license provides, making it insufficient for operating a commercial vehicle independently. Therefore, maintaining possession of the CDL is crucial for anyone driving a commercial vehicle.