Phil wrote:
Offramp writes:

If only a couple of people are walking up the left-hand side then the
escalator can only be working at 50% capacity. At busy times
escalators would be more efficient if standing on both sides were
compulsory. The tourists are right.

They would be even more efficient if everybody walked up them.

I don't know for sure, but wonder whether people walking up the escalator
tend to stay further apart than those who stand still? If so, walking may
actually reduce the capacity.