Some time back I approached a cyclist from behind that had a blinky on the back of their helmet. I liked the way you could see it from more than a couple of cars back because of the height. The one on the rack is harder to see for the 2nd, 3rd, or more car back in the line simply because it is blocked from their view. I have started running the light on the rack on steady and the blinky up high. Same thing on the front. Steady on the bars, white blinky on the helmet.