Where’s this train going?

In Barcelona…

…and Paris

Foreign tube/metro/subway systems can be confusing. This is a really low-tech but highly-useful solution for indicating to passengers which direction the train is travelling in. The lights come on as you pass through stations.

Most recently I was appreciating it on a trip to Paris, but I know it’s a system used in Barcelona too (and lots of other tube systems judging by a google search). Not London. Yet?