I would surmise that most of the car/bike accidents involve inexperienced cyclists not wearing helmets, not obeying traffic laws, intoxicated, etc. However, I am continuously amazed by "serious" cyclists that I see wearing dark clothes in low light conditions, with no tail lights or reflective gear, and acting like they own the road. My main criteria when I buy a new jersey is how visible it is -- thus, I've got quite a collection of orange, yellow and red jerseys. My commuter bike has 3 tail lights and a bright LED head light, and I always wear my very brightest jerseys in traffic.