Why is the low air pressure warning required to activate well above the pressure where the spring brakes would apply?

Pick an answer

1. To give the driver time to stop safely before losing air brakes entirely to the spring brakes taking over
2. To warn the driver that the fuel tank is almost empty
3. Because the spring brakes activate at a higher pressure than the service brakes, though that is not correct
4. To signal that the parking brake has been engaged manually

Correct!

Not quite. The correct answer is highlighted.