I had to Google "travelator".

I walk, and it's a total pet peeve of mine when people block the entire thing. Because I realize the customs may differ around the world, I think there should be signs above each escalator or moving walkway: stand on this side, walk on that side.

Maybe on a really long up escalator, I'll stand. I don't necessarily walk the entire way out of a deep London Underground station. But people should know where to stand so that walkers can get by.