A CDL endorsement is an additional certification that allows a commercial driver to operate specific types of vehicles or transport certain types of cargo. These endorsements are added to a Commercial Driver's License (CDL) and are required for drivers who want to operate vehicles like buses, tankers, or vehicles carrying hazardous materials. There are several types of endorsements, including the P endorsement for passenger transport, the N endorsement for tank vehicles, and the H endorsement for hazardous materials. Each endorsement requires passing a written test and, in some cases, a skills test to ensure the driver is qualified for the specific vehicle or cargo type.