Ah, but they think they're OK because they're riding in the gap between the double-yellow lines so they're out of harm's way...
Overtook one this morning who was invisible until I was up close - no lights, black helmet, black jacket, black waterproof trousers. They really don't stand out against a dark background, even with AyUps on.
I shouted "your lights aren't working" as I passed. I hope that's a less aggressive sounding shout that "Oy mate !!! Get some LIGHTS if you're riding in the dark on a busy road dressed in black !!"