There are reasons that we have helmet laws in this country. It's because they save lives. Even low speed accidents can lead to deadly head injuries when helmets aren't worn.
Today, I found out that my step-son's little brother was in an ATV accident when he wasn't wearing a helmet. He and his little sister were in a go-cart being pulled behind an ATV when the go-cart crashed into a concrete pole. Both children flew out of the go-cart. The girl was thrown clear, but the boy flew head first into the concrete pole. The girl had no injuries, but the boy had severe head injuries and was declared brain-dead yesterday. Though we'll never know for sure, he may have survived if he had been wearing a helmet. Or a seat belt.
My step-son was present for and witnessed the entire event. As I'm sure you can imagine, he's having a pretty difficult time dealing with it all.
Some good did come from this tragic event, though. The boy's organs were donated and helped to save several other children's lives. Organ donation is literally giving the gift of life. If you are not already an organ donor, I urge you to become one.