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 Oregon Commercial Driver.. 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 Oregon Commercial Driver 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 need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question 20

Passing Score 16

15. Push in the trailer air supply control to:

Activate the emergency brakes.

Deactivate the air brakes.

Sound the horn.

Supply the trailer with air.

Push in the trailer air supply control to supply the trailer with air. Pull out the trailer air supply control to turn off the air supply and activate the emergency brakes.

16. The trailer hand valve:

Should always be used for parking.

Should only be used for parking on a downhill.

Should never be used for parking.

Should only be used when transporting cargo.

The trailer hand valve should not be used for parking. This could cause all of the air to leak out of the braking system, resulting in the brakes releasing. Instead, use the parking brake.

17. If the emergency air line loses pressure:

The Anti-Lock Braking System will activate.

The service air line will activate.

The emergency brakes will activate.

The emergency air line controls the emergency brakes on a combination vehicle. A loss of air pressure in the emergency line will cause the emergency trailer brakes to activate.

18. The emergency air line:

Is controlled by the foot brake.

Is connected to the relay valves.

Supplies air to the trailer air tanks.

Prevents skids.

The emergency air line (also known as the supply line) has two functions. The first is to supply air to the trailer air tanks on a combination vehicle, and the second is to control the emergency brakes.

19. During a trip, which shut-off valves should be open?

All shut-off valves should be open.

The rear shut-off valves should be open.

All shut-off valves should be in the open position, except the rear shut-off valves.

No shut-off valves should be open.

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 the air is not able to escape from the back of the vehicle.

20. The trailer hand valve should:

Be used for parking.

Be used only to test the trailer brakes.

Be used together with the brake pedal.

Be used on slippery surfaces.

The trailer hand valve works the trailer brakes but should only be used when testing them. Using it while driving could create a skid. Never use the trailer hand valve while parking because doing so may release the air pressure from the braking system, releasing the brakes that are holding the vehicle in place.

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