Instructions

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.. Read More

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 20

Passing Score 16

15. Look into the back of the fifth wheel:

While testing your air brakes.

If your vehicle begins to skid.

When inspecting a coupling.

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:

Pulling the yellow, diamond-shaped knob.

Releasing air with the brake pedal.

Unlocking the trailer doors.

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:

Prevent air from escaping air brake systems.

Prevent air from entering air brake systems.

Override vehicles that are out of control.

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:

The vehicle will increase speed.

The trailer emergency brakes will be applied.

The air supply to the trailer will increase.

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:

You can assume all vehicles are the same.

Be sure that you are coupling correctly.

Cracks in the mounting are acceptable.

Incorrect coupling and uncoupling of combination vehicles can have extremely dangerous consequences.

20. During a trip, the ____ should be open.

Rear service line shut-off valve

Rear supply line shut-off valve

Inner shut-off valves

When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that it is not able to escape from the back of the vehicle.

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