[gsnedders]

They already have, e.g. adverts that run in parts down escalators. If you know plenty of people go from one corridor to another, you could extend such segmentation across corridors.

I imagine they can also do differential pricing of adverts across more of the stations with a better idea of footfall (though simple point footfall figures can be got in simpler ways), and indeed that is apparently part of what they're doing.