There are two types of car accidents, one in the car and one out of the car. The one out of the car that can kill you is probably accidental. People have accidental car crashes all the time, but what if it's not an accident, what if the other driver is trying to kill you.
The other guy gets one chance to kill you on a busy highway or in the city. You can blow this post off if you want, just because you don't think something will happen doesn't mean it wont.
First off let's talk about the accidental one people get ran over all the time and some of the survive so don't, some live and get badly injured some don't. pick which one you want to be. there are three ways to hit a car. A direct hit which will cause severe leg and hip damage, cause you to roll over the car, fall behind it, throwing you into more oncoming traffic. The second way is under the car, which I never recommend letting a 5000 pound or more vehicle run you over >_>.
The best way to survive a car accident or take the least damage is to go through the windshield like jumping on a trampoline a windshield buckles inward when hit from the outside. It doesn't take much to make it cave in, and you would land inside the car, so this is the best option.
Now let's talk about an accident from inside the car. Most cars now a days come with air bags, but what if they don't or you don't repackage the air bags. Plus if the person is trying to kill you or it is a semi truck, you don't want that airbag to deploy. You there are two options one with out a passenger and one with. You need to get down in the passenger seat and put your head in the crease of you arm where your elbow is and wrap the seat belt around your arm, whiplash can lead to severe neck damage or death.
Now if you have two passengers, you need to do the same as if one person, but the second must get in the back seat and lay down in between the front and back seats. once again restricted head movement must be used, this is not for normal accidents, I am talking if someone hits you and tries driving you into a concrete wall, and semi trucks take six seconds at 65mph to come to a complete stop you will have a little bit of time to do this. Use it wisely, like I said, blow this off if you want, but I told you how.