For one winter in the early 80s I biked everywhere in Huntington Beach on a cheap Sears bike that was too small and without any safety gear. I worked at a hospital every day and one day I finished my commute to work in an ambulance. I was holding a light in one hand when my front wheel hit a pothole and turned sideways, sending me over the handlebars. I'm sure I had a concussion but at the time they released me once I could answer questions.
Now I always wear a helmet and the light is attached to the bike. If only I could get my college aged kids to wear helmets.