Having been rear ended and blown out the rear window of the truck with my head I can say it wasn't that bad actually.

The glass is a safety glass (I've shattered several accidently, verifying this), and the whole window pops out quite nicely.

The thing to fear actually is you shooting out from under the seat belt, which I did. The rear seat mount collapsed in the wreck, and I went partially out the rear window.

This was with an old rusty early 80's truck. But the events would be the same for a new truck.

'97 T-100 SR5
'86 Toyota's, the variety pack (all gone)