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 Washington State Department of Licensing Commercial Driver Guide. 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. 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.

2. What is a bobtail tractor?

A tractor without a semi-trailer

A tractor with two semi-trailers

A tractor that travels faster than the speed limit

Tractors without semi-trailers are referred to as "bobtail tractors." Bobtail tractors are difficult to operate and drivers must exercise caution.

3. The trailer hand valve:

Should always be used for parking.

Should only be used for parking on a downgrade.

Should never be used for parking.

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. Instead, use the parking brake or wheel chocks.

4. Watching the road ahead:

Is more dangerous than only watching your mirrors.

Does not help you drive more safely.

Can help you avoid the need for sudden lane changes.

Making a sudden lane change can be dangerous while driving a combination vehicle. You can avoid the need to make a sudden lange change by looking down the road for upcoming obstacles that will require you to change lanes.

5. Older trailers are not equipped with spring brakes. This means that if the air supply for a vehicle's air braking system leaks away:

The trailer will stop normally.

The trailer will not have brakes.

The trailer will speed up.

Older trailers do not have spring brakes. This means that if the air supply in an older trailer's air tank has leaked away, there will be no working brakes connected to the trailer and its wheels will turn freely.

6. The emergency air line supplies air to the:

Relay valves.

Trailer air tanks.

Signal line.

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

7. Before beginning a trip, you should:

Leave the service line valve open.

Remove the relay valves.

Close the emergency line valve.

Before a trip, you should ensure that air reaches all air brakes on all trailers by opening up the rear emergency line and service line shut-off valves and listening for escaping air. Close both shut-off valves before beginning to drive.

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