It is the ability of the card to track real time movements of people collectively - ie the flows past the readers and therefore cardholders' presence shortly after on platforms - which is useful, I think.

I have noticed on the Tube that trains often seem to terminate early (to shuttle back), and re-route on an ad hoc basis - eg at an intersection like Camden Town on the Northern Line - far more than they used to.

I suspect that sophisticated analysis of people flows from Oyster data may be driving this traffic management.

A Diary from Bruce McF or DoDo on this might be interesting.

"Any economic unit can emit money. The serious problem is to get it accepted" Hyman Minsky