C3PX said:
No, I didn't mean decapitated by the seatbelt, I meant decapitated by the windshield from not wearing a seatbelt. Head goes through the windshield, and the glass cuts it off as the weight of the body pulls it down.
Oh, I see what you're saying now. That scenario is also completely impossible in every car manufactured after 1927. Those windshields and windows are made of safety glass so they shatter to a million pieces when impacted, sure they can cause small cuts, but they could never remove a limb or head. Glass in cars doesn't work like window panes in houses, they don't shard or have points. Once a cars window is busted, it will break apart real easy. I can clear a whole windshield out in under 10 seconds with my baton by scraping the edges of the frame. But the odd thing is that it holds people in the cars usually, they bounce off of it. Here's a good little write up on how safety glass works.
http://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/question508.htm