You are driving when your power steering stops working. You should:
Honk your horn and turn off the ignition.
Turn on your hazard lights and brace yourself.
Work hard to steer, reduce your speed, drive to a safe area, and stop.
Slam on your brakes.
If your power steering stops working, additional effort will be required to maintain steering control. Reduce your speed and pull off the roadway to stop in a safe area.