Also, the cars are required to roll in the air 360 degrees.
Believe it or not, I actually saw this happen in real life once.
I was driving through an intersection not long after the light had changed, and I heard a loud *CRUNCH* noise to my right. I turned my head to look out the side window just in time to see a mid-sized car pirouette through the air as gracefully as a ballerina, no farther than fifteen feet from my car. At the time I saw it, no part of the car was touching the ground, the lowest part of the car (the rear edge of the trunk) was at least two feet off the ground.
Of course, it quickly made an ungraceful landing... It ended up resting on the roof, and the driver (a middle-aged woman) was left dangling from her seat upside down, since she had her seat belt on. I stuck around to help (okay, and to gawk) as rescue workers quickly arrived and sawed the car apart so they could extract her easily.
The funny thing is that none of the cars involved had been going over 30 miles per hour. The woman's car ran a red light coming out of a convenience store parking lot, right into the path of our oncoming traffic, and managed to get hit just right to flip the car like a tiddly-wink.