If the engine unexpectedly stalls while traveling at speed on a highway, what mechanical behavior must the driver be prepared for?

1. The car flips upside down instantly
2. Braking and steering become significantly heavier due to loss of vacuum booster and power steering assist (制动和转向助力丧失), but mechanical control remains possible with increased physical force
3. The tires lose all internal air pressure
4. The doors unlock and swing open automatically