This article is really interesting, and is something I've thought about quite a lot. In the list of events during a 50km/h crash, the really cool bits are:
70 ms - Airbag continues to deflate. Occupant moves back towards middle of car.
Engineers classify crash as “complete”.
150-300 ms - Occupant becomes aware of collision.
If correct, this seems to mean that at best you detect a crash nearly 0.1s after the whole thing finishes. In the event of a fatal collision, then, it seems like you are almost certain not to experience it. Excellent.