It's not hard to be going fast inadvertently. The worst bike accident I was in involved me coming down a hill, stopping at the bottom on what turned out to be a

It's not hard to be going fast inadvertently. The worst bike accident I was in involved me coming down a hill, stopping at the bottom on what turned out to be an invisible bump, and flying over my handlebars. I broke my collarbone upon landing, but if I hadn't been wearing a helmet it would have been a lot worse. It just seems foolhardy to me to ride a bike without a helmet, like driving a car without a seatbelt.