I think that at the Union Square NQRW stop it’s purposely designed so that the windows which tell you what train it is are the FURTHEST from the bottom of the stairs. Usually I can tell if it’s an N or a Q based on if it’s a new train or not, but not all the N trains are new and there are a few new Q trains in service now too. I’ve got on a few times not knowing if it was one or the other since if I’m wrong I can just get off at Canal st. This guy I saw though got off as quickly as he got on after running down the stairs.