it's down to luck, i know a lad who has survived two accidents because he didn't have a seatbelt on, one was a pole through the window which whould have gone through his face if he didn't move, the other time i think he was just that drunk he did the whole baby thing a went limp. Muppet!
If you talk to most lorry drivers they don't wear a seatbelt as they think it's safer.