That would really only be feasible if a cyclist could safely make such a judgment while keeping their eyes on the road. If as a cyclist I'm holding up more tha

That would really only be feasible if a cyclist could safely make such a judgment while keeping their eyes on the road. If as a cyclist I'm holding up more than 6 cars behind me it's because whoever is in charge of building/ maintaining the road wasn't doing their job. I'd also say I've seen plenty times where cars have held up 20+ cyclists and given no indication they intend to let them pass.