How is the low air pressure warning usually tested as part of the pre-trip air brake inspection?

Pick an answer

1. By fanning or applying the brakes with the engine off until pressure drops to the warning point and confirming the alert activates
2. By listening to the engine at idle for unusual noise
3. By inspecting the tire tread depth
4. By confirming the warning bulb glows a certain shade with the ignition switched off and the engine cold

Correct!

Not quite. The correct answer is highlighted.