I know for sure that a bike helmet saved my life.
about 15 years ago I was rear ended by a car, I flew foward and landed on the rear wheel then crashed down, hitting my head. my helmet cracked, as it is supposed to do. I rolled right, off the road. the car that hit me was then hit by the car behind him, and the car then rolled over my bike, crushing it. if I hadn't rolled to the side, I would have been killed. if I hadn't had a helmet, I would have been in no condition to roll off the road fast enough to get out of the way.
helmets save lives