For years I have been commuting in Scotland in the dark and in winter, I should not say that in Scotland "sometimes" rain. With this combination of factors, riding in town, your tail red light (no matter how good it is, fixed or flashing) is just another red point within a myriad of other tail red lights of moving cars and red reflectors of parked cars, that drivers see with difficulty when the rain hits their windscreens. So even knowing that it was not legal I was commuting in the dark with an extra white flashing light (Petzl) attached at the back of my helmet and pointing backwards (besides the legal front white and fixed red tail lights, plus an illegal flashing tail red light). The helmet white flashing light facing backward was a real safety bonus, as it stood out of all red lights. Sometimes in crossings I switched the front light to strobe mode, drivers were not happy. I was/am selfish, my safety first, but I do not think that this configuration of lights can cause any accident to motor drivers, and being a driver too, I would not blame any cyclist that for their own safety is using an illegal but reasonable set of lights
