I can't figure it out. I can be going at top speed and run into something and take NO physical damage and stay in the driver's seat. Other times I'll be travelling not very fast at all, and hit something not even stationary, and go flying through the windshield. Sometimes you SURVIVE it, even if you're low on health. Sometimes even FULL HEALTH and FULL ARMOR, you get KILLED before your body even touches the GROUND. What is the issue with these "Through the Windshield" occurances. I like how if you sit on a motorcycle for a few seconds without moving that you put a helmet on. How about add the same thing to a vehicle, but have it be if you sit in it for 3 seconds before moving, you BUCKLE YOUR SEATBELT. If the seatbelt were part of the game, I can guarantee a lot of people would use and appreciate the function. Especially in online play. Since it seems to happen at random I can only imagine that it happens at the WORST possible times for most players and must seem totally unfair, like the game has been rigged against you.
EDIT, Suggestion for Death by Flying Through Windshield:
SON OF A BITCH ROCKSTAR!!!! If you are going to cause random deaths by having people fly through the windshield, at least let the whole scene play out!!! If I'm going to get killed flying through the windshield, I want to see the body fly as far as it will, hit the ground, leave a blood stain, bounce, tumble, roll and then die. As it is now the game starts loading you at the hospital before the body hits the pavement. That is totally ridiculous. Let the death scene play out!!!!!!