If power steering assist suddenly fails while driving (hydraulic belt snap or electric assist error), how does the vehicle behave and what should the driver do?

1. The steering wheel spins uncontrollably by itself; driver must let go completely
2. Steering effort becomes extremely heavy (转向沉重), but mechanical control is still intact; driver must grip the wheel firmly with both hands, use greater physical force to steer to the side of the road, decelerate, and stop safely
3. The front wheels detach from the axle
4. The brake pedal is automatically locked solid