Trailers can overturn as a result of the "crack-the-whip" effect. The last trailer in a combination is the most prone to tip over due to this effect. Drivers should be aware of the rearward amplification of their specific vehicles and drive accordingly.

Be more effective than braking.

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.

Should never be used for parking.

Should always be used for parking.

Should only be used for parking on a downgrade.

Should never be used for parking.

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.

The trailer will not have brakes.

The trailer will stop normally.

The trailer will not have brakes.

Before a trip, ensure that air in the air brake system reaches all trailers. Do this by waiting for air pressure to build, then sending air to both the emergency and service lines and opening the shut-off valves on the rear of the last trailer. If air escapes from the shut-off valves in the rear of the combination, the air is being supplied to the entire vehicle.

Listening for air at the rear shut-off valve.

Checking for moving air inside of each trailer.

Listening for air at the rear shut-off valve.

Feeling for air at the front shut-off valve.

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

More difficult to drive than single commercial vehicles.

Easier to drive than single commercial vehicles.

Lighter than single commercial vehicles.

More difficult to drive than single commercial vehicles.

Positioning the weight of a load on one side of a trailer may cause the trailer to lean to that side, increasing the risk of a rollover during turns and lane changes.

May add extra support during turns.

May be easier to steer during turns.

Combination Vehicles Practice Test | Louisiana 2025 #1

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 2025, 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 2025 #1

1 . The "crack-the-whip" effect can:

2 . The trailer hand valve:

3 . When testing ____, you should apply your vehicle's brakes with the hand control while moving the vehicle forward slowly.

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

5 . Before a trip, you can make sure air flows to all trailers by:

6 . Combination vehicles are usually:

7 . If a load is placed on one side of a trailer, the trailer:

See the exact questions that will be on the 2025 DMV exam.

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