I agree with the notion that we are more visible on dark roads than when competing with a bunch of lights. I also think DX has it right about the drivers getting worse as the weather gets bad. We don't get much snow here (maybe one inch per year), but it started snowing five minutes ago. Three minutes ago I heard the local ambulance head up the road to do its business. When the rain starts, siren. When the snow starts, siren. When the sun comes out, siren. When night falls, siren. Needless to say, I hear a lot of sirens (about a dozen per day).