Answer :
Final answer:
The tractor protection valve in an air brake system typically needs to activate before system pressure drops below 20 to 45 psi to ensure there is enough air pressure for the tractor to stop safely.
Explanation:
The tractor protection valve is a critical component of a tractor-trailer combination's air brake system, designed to prevent air loss in the event of a trailer breakaway or major leak. The valve system must activate before the system pressure falls below a certain level to ensure safety. While the exact pressure level for a tractor protection system to engage might vary depending on specific regulations and systems, it is commonly accepted that the tractor protection valve should activate before the system pressure drops below 20 to 45 psi (pounds per square inch). This range ensures that there is still enough air pressure remaining in the tractor to enable the driver to bring the vehicle to a safe stop while also protecting the air supply to the tractor's brakes if the trailer's air supply is compromised.
