Noticed these around London yet?

Pink card readers at some Tube and London Overground stations tell us which route you’ve taken so we can charge you the right fare. Some routes are cheaper than others, such as those which avoid Zone 1.

When to use the pink card readers

If you’re using pay as you go or have a Travelcard that doesn’t include Zone 1, you may need to touch on a pink card reader when changing trains at one of the stations listed below to pay the right fare.
https://tfl.gov.uk/fares-and-payments/oyster/using-oyster/pink-card-readers