Combination
All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial Driver License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will have two hours to correctly answer a minimum of 16 questions. The Combination test is not a replacement for the Double/Triple endorsement test.
Number of Question
Passing Score
15. Look into the back of the fifth wheel:
Explanation
While inspecting a coupling, you should go under the trailer and look into the back of the fifth wheel. Ensure that the fifth wheel jaws are secured around the shank of the kingpin.
16. A driver should test the tractor protection valve by:
Explanation
You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.
17. Shut-off valves:
Explanation
Shut-off valves are used in air supply lines to control the passage of air from one trailer to another. The rear shut-off valve should always be closed to prevent air from leaving the braking system.
18. If an air supply control is in its "emergency" position:
Explanation
Tractor protection controls in older vehicles may be operated by levers instead of knobs. If an air supply control is set in its "emergency" position, the air supply will be stopped and the trailer emergency brakes will be applied.
19. When coupling:
Explanation
Incorrect coupling and uncoupling of combination vehicles can have extremely dangerous consequences.
20. During a trip, the ____ should be open.
Explanation
