This subway station was originally constructed with ONE such subterranean "pedway" passageway southward under Clybourn to "Dayton Street", at the mezzanine level, and is so marked with ceramic tile lettering. It was "exit-only" but, were it not abandoned and plugged up, could have been used today as a farecard entrance like the reopened Polk Street entrance to Harrison Red Line Station (which still has ceramic tile letters reading "Dearborn Station").
I think one or two of the multiple Grand/Milwaukee Blue Line "pedway" entrances also got plugged up in later years. Grand/Milwaukee was closed altogether for a number of years. It was the only subway station in Chicago ever to be abandoned outright (not counting the Washington/State stop on the Red LIne or the south entrance to Jackson/State, between Van Buren and Congress (which had been constructed with an entrance to the former Sears, Roebuck & Co. department store).