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.

Before a trip, be sure to inspect all couplings. There should be no space between the upper and lower fifth wheel.

A maximum of two inches of space

When coupling air brake hoses, you should make sure the proper pairs of gland hands are connected. They are sometimes color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

Make sure to couple the proper glad hands.

Only couple one set of glad hands.

It is best to leave one glad hand loose.

Shut-off valves are used in air supply lines to control the passage of air from one trailer to another. The rear shut-off valve should always be closed to prevent air from leaving the braking system.

Prevent air from escaping air brake systems.

Prevent air from entering air brake systems.

Override vehicles that are out of control.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

The tractor protection valve will close.

The service brakes will activate.

The tractor protection valve will close.

The rear trailer will detach from the combination.

Combination Vehicles Practice Test | Missouri 2024 #1

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 #1

1 . A tractor protection valve:

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

3 . How much space should be between the upper and lower fifth wheel?

4 . When coupling, you should:

5 . Shut-off valves:

6 . If the emergency air line loses pressure:

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

Search the best driving school in your neighbourhood

Wait, before you go