You must have a passenger (P) endorsement on your CDL to drive a vehicle with 16 or more occupants including yourself. To obtain this endorsement, you must meet several requirements including passing a knowledge test and a skills test in a vehicle that is representative of the class of vehicle you will be driving professionally. The knowledge test covers safe commercial driving and safe transportation of passengers. These subjects are covered in chapters 2 and 4 of the official state CDL manual. Note: If you plan to drive buses with air brakes, you must also pass a separate knowledge test and skills test on air brakes. Otherwise your CDL will include a restriction prohibiting you from operating vehicles with air brakes.