In my case it was another of those "slow motion" events. As soon as I started sliding forward, I knew I was bound for the pavement. And the car was still rolling at that point. It doesn't take long to realize the imminent problem. I can remember focusing on getting a grip on the bumper in case that was all between me and being flattened. I didn't relish the thought of being dragged but it beat the hell out of any alternative I could see. Luckily the driver foresaw the same outcome I did.In high school a friend jump on the hood of my car and was almost immediately thrown off. He was athletic enough that he rolled properly and wasn't injured, but it shook him, me, and everyone in the car with me enough that I doubt any of us ever participated in such stupidity again.