[matthewmacleod]

"Targeted advertising" in the sense of real-world, physical targeting. Like, where should adverts be placed in the station to maximise exposure.

That doesn't require and collection of data, and they have explicitly ruled out doing such collection.

[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.