that say "21 Street–Queensbridge." Above this is a thin black strip of metal and above this are yellow squares that take the platform walls up to the station ceiling that is made of concrete. There are no columns between the two tracks or on the platforms, except near the mezzanine and overpass. As with other stations constructed as part of the Program for Action, the 21st Street–Queensbridge station contained technologically advanced features such as air-cooling, noise insulation, CCTV monitors, public announcement systems, electronic platform signage, and escalator and elevator entrances. Exits Outside of fare control, the mezzanine leads to two street stairs at the northeast corner of 21st Street and 41st Avenue. An elevator and escalators are at the northwest corner of the same intersection. Track layout Until the connection to the Queens Boulevard Line opened, this station shared the characteristic of a two side platformed terminal station with Flatbush Avenue–Brooklyn College on the IRT Nostrand Avenue Line. This is an inefficient terminal setup, requiring passengers to know which track the next train will depart from before going to the platform level. As a terminal from 1989 to 2001, the station had tail tracks that continued eastward as far as 29th Street, ending at bumper blocks. Also, this station has "punch boxes", with buttons to indicate route selection to the train dispatcher; a control tower on the west end of Manhattan-bound platform, which can be used if necessary; and a diamond crossover switch to the west which was used to turn trains. Stub tracks east of the station East of the station, before the line connects to the IND Queens Boulevard Line, the tracks veer left while the tunnel wall goes straight, stopping around Northern Boulevard. This bellmouth is part of an intended "super-express" bypass of the IND Queens Boulevard Line running along the mainline of the Long Island Rail Road between Queens Boulevard and Forest Hills–71st Avenue planned in 1968. At a proposed station at Northern Boulevard, for which the 29th Street tail tracks might have also been built, a transfer concourse to the Queens Plaza station would have allowed transfers between local, express, and bypass trains. The current bellmouth, built along with the Queens Boulevard connection, is two levels deep with two additional stub-end subway tracks named T1A and T2A. It is viable for future construction of the bypass or the Northern Boulevard transfer station. The original bellmouth