@coolboymew @lanodan Yeah, I don't know why they did it. There must be a reason. In Tokyo, doors in barriers appeared on the busiest stations first, primarily because their platforms were too narrow, and it was possible for people get squeezed out on the tracks. I think 2013 was the first time I saw them, and only in places like Akiba, Kanda, etc. on Yamanote. The first photographic evidence that I have is from 2015: