turning southeast under private property. The small 174th Street Yard lies under Broadway, with two tracks exiting to the south under that roadway. When the George Washington Bridge was designed in the 1920s, provisions were made for a lower deck that would carry these two tracks north from the yard and across the bridge, as well as two commuter rail tracks. However, when the lower level was added in 1962, it instead carried a roadway. The two main tracks from Fort Washington Avenue enter Broadway near 172nd Street, curving and running underneath a public school (PS173M) at 174th Street, and other private property, and the yard tracks in a double-decker tunnel. A few blocks later, the lower tracks separate to straddle the yard tracks at 168th Street. The local/express split begins here, with the local tracks coming from the yard and the express tracks coming from Inwood. Contrary to standard practice, the two local tracks are in the center and the two express tracks are on the outside. Except during late nights, the local service (C) ends at 168th Street, reversing direction on the yard tracks; the A runs to 207th Street at all times, express except during late nights. South of 168th Street, the express (outer) tracks lower below the local tracks, forming another double-decker tunnel, this time under St. Nicholas Avenue. North of 145th Street, the lower (express) tracks rise into the center, and the three-track IND Concourse Line enters St. Nicholas Avenue below the four-track Eighth Avenue Line. 145th Street is a two-level transfer station, with two island platforms on each level. To the south, the Concourse Line tracks rise and merge with the Eighth Avenue Line, carrying the B onto the local tracks and the D onto the express tracks. The resulting four-track line continues south under St. Nicholas Avenue and Eighth Avenue (Frederick Douglass Boulevard), which becomes Central Park West at 110th Street. Most of the line under Central Park West is built on two levels with both local tracks to the west and only local stations. The two northbound tracks are above the two southbound tracks. Approaching 59th Street–Columbus Circle, where Central Park West becomes Eighth Avenue, the subway again spreads out into a single four-track level. A flying junction south of 59th Street takes B and D trains east under 53rd Street, merging with two tracks from 57th Street to become the four-track