I would still use "on".
Retired English Teacher
"During the flu season, we had better often wear masks in the crowded space, such as (A. in, B. on) the bus or train in the rush hour."
I know we usually say "on the bus or on the train", but the parenthesis in the sentence above refers back to "the space", I wonder whether "in" is a better choice. Thank you a lot.
I'd use on, but in is OK.
BTW in the crowded space doesn't work- try in crowded spaces.
***** NOT A TEACHER *****
"During (the) flu season, we should wear masks in crowded spaces, such as those [i.e., crowded spaces] that are found on buses and trains."