What function does the tractor protection system serve?
- It increases air pressure when the trailer is disconnected
- It prevents the total loss of air from the trailer if the tractor breaks away
- It reduces air pressure in the event of a sudden stop
- It prevents the total loss of air from the tractor if the trailer breaks away, or if the connecting air lines between tractor and trailer are separated or ruptured ✓
Answer: D. It prevents the total loss of air from the tractor if the trailer breaks away, or if the connecting air lines between tractor and trailer are separated or ruptured
The tractor protection system prevents the total loss of air from the tractor if the trailer breaks away or the connecting air lines separate or rupture.
Why this is the answer
The handbook explains that when the trailer separates, the connecting air lines break and air from the tractor can rush out through the broken supply or control line. The tractor protection system automatically shuts off that air loss from the tractor, keeping enough pressure for the driver to make a safe stop. Some systems shut off immediately, while some allow tractor pressure to drop before shutting off. That matches protecting the tractor air supply when the trailer breaks away or the lines separate.
Why the other answers are wrong
- A. It increases air pressure when the trailer is disconnected — The system shuts off air loss from the tractor; the passages do not say it raises pressure when the trailer is disconnected.
- B. It prevents the total loss of air from the trailer if the tractor breaks away — The protection described is for the tractor air supply; the passages say the trailer's emergency system applies trailer brakes, not that this system prevents total loss from the trailer.
- C. It reduces air pressure in the event of a sudden stop — A sudden stop is not what activates it; it responds to trailer breakaway or separated or ruptured lines, not to reducing pressure during a sudden stop.
Remember it
Remember that this valve protects the tractor's air supply, not the trailer's.