this station has two side platforms and three tracks, the center one being an unused express track. the southbound local track is technically known as bb1 and the northbound one is bb4; the bb designation is used for chaining purposes along the broadway–seventh avenue line from 96th street to 242nd street. although it cannot be accessed at cathedral parkway–110th street, the center track is designated as m. these designations are rarely, if ever, used in ordinary conversation.