What is the tractor protection valve, and why is it checked during the air brake inspection?

Pick an answer

1. It automatically protects the tractor's air supply if the trailer's air system fails or separates
2. It protects the tractor's own brakes from losing pressure if the trailer disconnects, which isn't obvious without real inspection experience
3. It is a valve that only controls the tractor's horn system
4. It has no connection to the air brake system at all

Correct!

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