Like other local stations, 91st Street has four tracks and two abandoned side platforms. The two local tracks, which formerly served the station, are used by the 1 train at all times and the 2 train during late nights. The two express tracks are used by the 2 train during daytime hours and the 3 train at all times. The platforms were long, as at other local stations on the original IRT. While the local tracks stay level, the express tracks are at a lower elevation throughout most of the station.