Practice question

What is the function of the tractor protection valve in a semi-trailer air brake system?

It closes automatically if the trailer breaks away or air lines snap, preserving air pressure in the tractor so the driver can still steer and brake the tractor
It prevents the trailer brakes from being applied while the vehicle is reversing
It regulates the pressure supplied to the trailer down to a lower working value
It couples the tractor and trailer electrical systems together

Answer: A — It closes automatically if the trailer breaks away or air lines snap, preserving air pressure in the tractor so the driver can still steer and brake the tractor

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