Answer :
Final answer:
In a combination vehicle, if both air lines are pulled apart, the emergency brakes activate, and the tractor protection valve closes, ensuring the tractor maintains its air pressure and braking capability.
Explanation:
If you are driving a combination vehicle and the trailer is pulling apart both air lines, you should expect the emergency brakes to come on and the tractor protection valve to close. The trailer air supply is designed to automatically lock in this situation to prevent air loss from the tractor, ensuring that the tractor brakes continue to function properly. This is a safety feature to prevent the trailer from losing all air pressure which could lead to a loss of braking ability.
