If a heavy truck loses all pneumatic air pressure due to a catastrophic hose rupture while parked, what happens to the vehicle?

1. The truck rolls away freely down the hill because there is no air to brake it
2. The vehicle cannot be moved because the spring brakes (Federspeicher) lock the wheels mechanically; moving the vehicle requires emergency mechanical winding (Notlöseeinrichtung) or external air supply
3. The engine automatically accelerates to maximum RPM
4. The tires deflate instantly