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.

Close the emergency line valve.

Leave the service line valve open.

Close the emergency line valve.

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 the truck braking system if the trailer develops a leak.

Ensures that oil adequately lubricates the engine.

Protects the tractor from exceeding a set speed.

Keeps air in the truck braking system if the trailer develops a leak.

It is important that all of a vehicle's equipment is in proper working condition before beginning a trip. If a trailer's spring brakes do not release when you push in the tractor air supply control, you should make sure the air line connections are properly attached and sealed.

Inspect the air line connections.

Activate the Anti-Lock Braking System.

Turn the engine off and on again.

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.

Never use the trailer hand valve while operating your vehicle. Using the trailer hand valve while driving can cause your trailer to skid.

It will disconnect from the vehicle.

You will stop the vehicle too quickly.

Combination Vehicles Practice Test | Missouri 2024 #2

Train for FREE online with our Missouri 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 MO 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 | Missouri 2024 #2

1 . Before beginning a trip, you should:

2 . If color-coded, which color is used to identify service lines?

3 . The tractor protection valve:

4 . If you press the tractor air supply control and your trailer's spring brakes do not release, you should:

5 . In a double or triple combination, the ____ trailer should be directly behind the cab.

6 . A tractor protection valve:

7 . The trailer hand valve should not be used while you are driving because:

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