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 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

1. What is a tractor protection valve?

A valve to keep air in the brake system should there be a bad leak

A valve that prevents a truck from being stolen

A valve that prevents the driver from driving too fast

A tractor protection valve keeps air in a tractor or truck air brake system should the trailer break away or develop a bad leak. The valve will close automatically if the pressure drops to an unsafe level.

2. In a combination rig, it is best to make:

Quick, sudden stops.

Sharp turns.

Quick accelerations.

Slow, planned stops.

When driving a combination vehicle, it is important to brake well in advance and look far ahead of your vehicle to avoid the need for sudden stops. Making habits of these actions will help you prevent your trailer from jackknifing.

3. What is off-tracking?

When a vehicle’s front wheels follow a different path than its rear wheels

When a vehicle's wheels all follow the exact same path

When a load shifts during a turn

When a vehicle's wheels run over a curb during a turn

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is known as off-tracking, or "cheating."

4. When braking while pulling a trailer equipped with anti-lock brakes, you should:

Pump the brakes.

Use extra braking force to ensure the brakes kick in.

Brake as you would without anti-lock brakes.

When driving a tractor-trailer combination that is equipped with an Anti-Lock Braking System (ABS), you should brake in the same manner that you would if the vehicle was not equipped with ABS.

5. 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.

6. Pushing in the trailer air supply control will:

Supply the trailer with air.

Deactivate the air brakes.

Prevent the vehicle from skidding.

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.

7. When should the trailer hand valve be used?

Only when the trailer is carrying a load

Only to test the trailer’s brakes

Only in inclement weather when the trailer may skid

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes. Using it while a vehicle is in motion could cause a skid.

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