In japan when you use escalators,
you should respect some rules in order to do not bother Fukuoka people.
This not an unwritten rule, but in Fukuoka when you are taking escalators,
usually people are lining up on the left side to let the right side open for people who want to walk up faster.
Each city has his own habbits, for example Osaka is the opposite of Fukuoka:
you should line up on the right side to let the left side open.
However, walking on escalators increase the risk of injuries and accident,
especially for eldery person who even by standing on one side could be unbalanced by people walking up.
So recently, officials in Japan have been pushing for a set of rules governing escalator :
"Do not walk. Stand on either side."
In Fukuoka subway, usually people still stand on one side to let the right side open,
but in malls when escalators are crowded,
I've ofter seen people standing on both side of escalators.
So you have the choice between respecting the residents habbits,
or respecting the security advices.