What does the tractor protection valve do?

Question

The tractor protection valve keeps air in the tractor or truck braking system, should the trailer break away or develop a bad leak.

Accepted Answer

Keeps air in the braking system, should the trailer break away or develop a leak

Answer

Protects the tractor from being stolen

Answer

Protects the tractor from exceeding a set speed

Answer

Ensures oil adequately lubricates the engine