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Free CDL Test Questions and Answers
Multiple-Choice Quiz

CDL SAMPLE COMBINATION PRACTICE TEST

Just click on the button next to each answer and you'll get immediate feedback.

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1. You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:

Trailer tank pressure to be lost.

Tractor spring brakes to lock on.

Service brake will come on

Trailer emergency brakes to come on.

2. If you are pulling an older trailer and cross the air line hookups, what will happen?

Nothing; the service and emergency lines are interchangeable.

The spring brakes will be activated.

The air in the service system will be emptied.

The brakes on the trailer will not work.

3. After coupling, when the full weight of the trailer is resting on the tractor, you should
check for enough clearance between the rear of the tractor frame and the landing gear and:

Clearance between the duals on the trailer.

Clearance between the top of the tractor tires and the nose of the trailer.

Clearance between the air tanks and the safety relief valve.

Air pressure in all the tires.

4. What is off tracking?

When a vehicle goes around a corner, and the driver pulls off the road.

When a vehicle goes around a curve and turns back the other way.

When a vehicle goes around a corner, the rear wheels follow the same path as the front wheels.

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels.

5. Relay valves:

Allow the trailer brakes to be applied more quickly

Signal the low air warning device

Reduce air pressure to the drive axle

Are not required on combination

6. The shut-off valves must be in what positions when pulling doubles?

lead trailer closed; rear trailer open; dolly air tank closed

lead trailer closed; rear trailer closed; dolly air tank open

lead trailer open; rear trailer closed; dolly air tank open

lead trailer open; rear trailer closed; dolly air tank closed

7. Which one of the following is controlled by the foot brake?"

The emergency air line

The shut off valve

The service air line

The hose coupler

8. Which one of the following statements about tractor protection valves is NOT true?

It keeps air in the tractor in the event the trailer air leaks

It is controlled by the trailer air supply valve in the cab

It will close automatically if air pressure is low

When it closes it allows air to leak from the tractor line

9. A device which connects the service and emergency air lines from the truck to the trailer is called:

Relay switch

Service couplers

Glad hands

Shut off valves

Counter