Many thousands of people are hurt every year in bicycle accidents, and hundreds die. Careful riding helps prevent accidents. When riding on streets, it is safest to ride on the same side of the street that cars drive (which would mean riding on the right side of the road in countries where people drive on the right side of the road, and riding on the left in countries where people drive on the left). To avoid hitting people, riders must obey signs that say "no bicycling", even if it does not seem to make sense at the time. Low light makes bicycle lighting important. It may not be safe to ride when it is dark. Riders wear reflective clothing to be safer in low light. Wearing a helmet makes bicycle riding safer. Wearing a helmet does not mean that somebody cannot be hurt if they crash their bicycle, but it makes being hurt less likely. Some bicycles have bells or horns that the rider can use to warn other people that they are riding by them.