A great solution to encouraging the right pedestrian traffic flows in busy public places. This from Sheffield Train Station. So there's dedicated stairs to go up and dedicated stairs to come down. To help reinforce the overhead signage there's "no entry" symbols on the steps (with equivalent arrows on the neighbouring ones).
Sure in crowds these might not be visible, but those crowds would start with light pedestrian flow. Something about "a stitch in time". There's also something here about the fact we tend to be careful and observe where we step if mostly with our peripheral vision, and this seems to play to that.
