Ralph Avenue on the has a closed entrance and partly closed mezzanine for Howard Avenue as well as Franklin Avenue (closed entrance for Classon Avenue) and a few other stops in Manhattan (Spring, 50th, 96th, 103rd, 116th, 155th, 163rd). I think these entrances were closed off as part of the TA's efforts to decrease crime on the subway system in the 80's and 90's.