Driving combination vehicles requires more skill than driving single commercial vehicles. Combinations are generally longer, generally heavier, and are more vulnerable to rollover.

Require more skill to drive than single commercial vehicles.

Often have taller trailers than single commercial vehicles.

Are usually lighter than single commercial vehicles.

Require more skill to drive than single commercial vehicles.

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.

Keeps air in a brake system if there is a bad leak.

Prevents a truck from being stolen.

Prevents a trailer from being accidentally released.

If your trailer begins to drift while you are backing, you should correct the drift immediately by turning the top of the steering wheel in the direction of the drift.

Turn the top of the steering wheel in the direction of the drift.

Return the steering wheel to the 12 o’clock position.

Turn the top of the steering wheel in the direction of the drift.

Turn the top of the steering wheel in the direction opposite of the drift.

Incorrect coupling and uncoupling of combination vehicles can have extremely dangerous consequences.

Be sure that you are coupling correctly.

You can assume all vehicles are the same.

Be sure that you are coupling correctly.

Cracks in the mounting are acceptable.

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.

Prevent the vehicle from skidding.

A trailer may swing out and strike other vehicles if its wheels lock up. This is especially likely with lightly-loaded trailers.

The vehicle will maintain steering.

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.

Only to test the trailer’s brakes

Only when the trailer is carrying a load

Only to test the trailer’s brakes

Only in inclement weather when the trailer may skid

Combination Vehicles Practice Test | Louisiana 2024 #1 Page 2 of 3

Train for FREE online with our Louisiana CDL combination vehicle test. The official exam test consists of several obligatory parts, with all of them checking your knowledge of different blocks of road rules. If you need to obtain a LA combination license in 2024, practice as much as possible. Free sample tests published on our website will help you check and improve your knowledge and boost your grades. Please bear in mind that DMV requirements for issuing a combination license may vary from state to state.

Number of Question 20

Passing Score 16

Number of Tests 20

Combination Vehicles Practice Test | Louisiana 2024 #1 Page 2 of 3

8 . Combination vehicles:

9 . A tractor protection valve:

10 . If you are backing and the trailer begins to drift off-course, the driver should:

11 . When coupling:

12 . Pushing in the trailer air supply control will:

13 . When the wheels of a trailer lock up:

14 . When should the trailer hand valve be used?

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