I'll just add that even with a helmet, don't expect to escape serious head and facial trauma every time. I work in an E.R. that treats lots of patients with trauma from bike accidents. Bicycle helmets, unlike motorcycle helmets, don't come down far enough on the head to protect the base of the skull; they don't protect the front of the face; and they don't protect the sides of the neck. Can it help? Sure, and around heavy traffic I'll wear one but I also know that 'back in the day' I wiped out a number of times without one and never had any head injuries.