What happens to the spring brakes if a vehicle loses enough air pressure while parked, even if the driver never touched the parking brake control?

Pick an answer

1. The spring brakes apply automatically once pressure drops low enough, holding the vehicle even without driver action
2. Nothing happens, since spring brakes only ever respond to the driver's own parking brake control lever
3. The engine restarts automatically to rebuild pressure before anything else happens
4. The vehicle's wheels are released completely, making it easier to roll away

Correct!

Not quite. The correct answer is highlighted.