A lot of those are going to be the same people day in and day out, the article says 500k faces, not people. You also have to filter out those people where the cameras aren't getting an image good enough to scan.

The article doesn't say, and I haven't seen the cameras, but it's not like you're getting every single person parsing through those stations.

But, yes, the numbers seems low.

BTP say [0] that "the images and biometric data of those who don’t cause an alert are automatically and immediately deleted." - if that's true, they shouldn't be able to tell that it's the same faces being scanned multiple times so it has to be 500k total scans rather than, say, 500k unique faces across 2 million scans

[0] https://www.btp.police.uk/police-forces/british-transport-po...

They're quite tall an positioned just after the barriers so I would believe they're quite effective on capturing faces. https://images.ctfassets.net/pjshm78m9jt4/29ok6Erlnhk6WIqP3w...