I use a flashing light only. However, I ride all city streets with decent lighting to see my way. The flashing light is just extra help to get cars to notice me when I am white lining through traffic, or waiting in the left turn lane in the intersection. Basically its my extra visibility for what i hope is added safety. I also live on a 2 way city street with no markings, and even though my time on that particular street is low, it sure is nice to really grab the attention of cars that are riding straight at me.