There's this wonderful story making the rounds about how an engineer in Washington used a basic knowledge of physics to save the life of an elderly driver passed out behind the wheel. You can read all about it at the Seattle Times. Mr. Innes saw the driver of a truck was passed out and heading for a busy intersection, but the vehicle was still going. So he took his van, got ahead of the truck and matched the speed. Then, decelerating, he let the truck rear-end him, and then used that contact to slow down the truck. The trick here is that while both vehicles were travelling fast, they were both travelling in the same direction, so at the time of the crash, the difference in speed was only a few miles per hour. This resulted in a much less dramatic crash, after which he could slow presumably by breaking thus avoiding a crash with a larger difference in speed (like 80+ mph).
In a bizarre show of humanity, Mr. Innes was told that he wouldn't have to cover damages for the collision. The Insurance Company promises not to act humanely twice.