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 25 multiple-choice questions, and applicants will need to correctly answer a minimum of 20 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question 25

Passing Score 20

7. The trailer hand valve should be used:

To test the trailer brakes.

To check the connection between the trailer and tractor.

To accelerate.

The trailer hand valve (also referred to as the "trolley valve" or "Johnson bar") works the trailer brakes and should be used only when testing them. Using the trailer hand valve while driving could result in a skid.

8. 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.

9. A loss of air pressure in the emergency line will cause:

The service brakes to activate.

The tractor protection valve to close.

The rear trailer to detach from the combination.

The suspension springs to extend.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

10. If a trailer's spring brakes do not release when you push the tractor air supply control, you should:

Check the air line connections.

Release the pintle hook.

Replace the spring brakes.

Drive normally without checking anything.

It is important that all of your vehicle's equipment is in proper working condition before you begin a trip. If a trailer's spring brakes do not release when you push in the tractor air supply control, you should make sure the air line connections are properly attached and sealed.

11. When entering or crossing traffic while driving a combination vehicle, it is especially important that you:

Sound your horn.

Make sure there is a large enough gap for your vehicle.

Expect other drivers to make room for your vehicle.

Let other drivers wave you into their lane.

Combination vehicles require more space on the road than other vehicles. When entering or crossing traffic while driving a combination vehicle, it is especially important that there is a large enough gap in traffic for you to safely do so.

12. A trailer will be most likely to swing around when:

It is full.

Traveling in a straight line.

It is empty.

The wheels are rotating.

An empty trailer will require a longer stopping distance than a loaded trailer. Additionally, a trailer is most likely to swing out and strike other vehicles when it is lightly loaded or empty.

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