The video below explains an experiment taking place in London. It's a long established tradition that when on an escalator if you want to stand still, you stay to the right but it you want to walk up, you go on the left. The people who walk are usually in a hurry and resent it if there is someone standing their way. But they are finding that the escalator can carry more people if people stand next to each other and ride instead of walking. The video explains it.
I wish them luck in changing the habits of millions of Tube riders.