IRT A Division
IRT White Plains Road Line
IRT Lenox Avenue Line at 135th Street and upward
Nostrand Junction (or Rogers Junction)
Just at the east end of the Franklin Avenue station on the IRT Eastern Parkway Line in Brooklyn is a two-level flying junction where trains can either continue on Eastern Parkway or diverge south to the IRT Nostrand Avenue Line. Further east, the northbound local track descends to a lower level directly below the southbound local track; then, the northbound express track, which is still on the upper level at this point, descends to the lower level directly below the southbound express track, creating a dual level two-over-two track layout. A switch on the upper level allows trains on the southbound express track to change to the local one and a corresponding switch on the lower level allows trains on the northbound local track to change to the express one.
Flatbush Avenue-Brooklyn College station
IRT Lexington Avenue Line between the Bronx and 116th Street station
[Second picture that features the track layout between 125th Street and 116th Street coming sooner or later]
IND/BMT B Division
[New picture coming sooner or later]
145th Street is a bi-level express station on the IND Eighth Avenue Line and the IND Grand Concourse Line in Harlem, Manhattan. Each level has four tracks and two island platforms. On the upper level, the band is gold with black border. The station had a full mezzanine, although the central portion is now used as a police precinct. On the lower level, the tile border here is gold with black and the name tablets are black with gold border. Escalators lead up from this level to the mezzanine, bypassing the upper level platforms.
On the upper level, just north of the station, there is an open space next to the uptown local track that was a remnant of the construction of the subway and not built for a specific purpose. That open space is where the lower level tracks turn off to the IND Grand Concourse Line. There is a hole in the floor that allows a view of the lower level. Just past the south end of the upper level platform is a crossover that allows local trains to change to the express track and just past the north end of the upper level platform is a crossover that allows express trains to change to the local track. South of the station on the lower level are diamond crossovers between all four tracks, allowing express trains to cross to the local track or local trains to cross to the express track. Just before entering the next station south, 135th Street, the lower level Grand Concourse Line tracks rises and merges with the Eighth Avenue Line tracks. At this point, through 135th Street, to just north of 125th Street, the line is now shorten from eight to six tracks. Express trains use the innermost pair of tracks while the locals use the outermost tracks.
South of 59th Street–Columbus Circle station on the IND Eighth Avenue Line
South of 59th Street–Columbus Circle station on the IND Eighth Avenue Line in Manhattan is a two-level flying junction where trains can either continue on Eighth Avenue or diverge east to the Seventh Avenue–53rd Street station via the IND Sixth Avenue Line express tracks. With this particular flying junction and overall track layout, a downtown Eighth Avenue train can never held outside north of the station by a downtown Sixth Avenue train. However, downtown Sixth Avenue trains are delayed inside the tunnel to let one proceed first before the other can continue behind; all uptown trains can still be delayed by each other depending if they're ahead or behind schedule.
Rockaway Boulevard station
The Rockaway Boulevard station in Ozone Park, Queens on the IND Liberty Avenue Line, which is served at all times by the A train and on summer weekend daytime hours by the extended Rockaway Park Shuttle, has three tracks and two island platforms rather than two side platforms. Trains going west to Brooklyn and east to Lefferts Boulevard or the Rockaways run on the outer tracks while the center track is used to terminate overnight shuttle trains from Lefferts Boulevard and seasonal shuttle trains from Rockaway Park. These trains discharge their passengers on the westbound (railroad northbound) platform, before the doors close and reopen on the eastbound (railroad southbound) platform to pick up passengers. It is the outermost station from Manhattan that is shared by all A train branches. Just past the east (railroad south) end of the platforms, the line splits into two routes. Trains going to Lefferts Boulevard continue east on Liberty Avenue while those going to the Rockaways turn south towards Howard Beach, Jamaica Bay, Broad Channel, and the Rockaways. Just past the west (railroad north) end of the platforms are a pair of diamond crossovers, the first connecting the westbound outer track to the middle one and the second connecting the aforementioned middle track to the eastbound outer one. These switches are used to short turn trains if there is a blockage anywhere (either the Lefferts Boulevard or the Rockaway branches, not referring to the Rockaway sub-branches south of Broad Channel). These are also the very same diamond crossovers east of 80th Street station in the real world, yet west of this station (here at Rockaway Boulevard) in my world.
IND Grand Concourse Line
The IND Grand Concourse Line runs north to south through the Bronx and portions of Harlem, parallel to the mostly-elevated IRT Jerome Avenue Line which lies between the two and four blocks to the west for its entire length in the Bronx. It begins as a two-track subway at Norwood–205th Street, running east-to-west underneath East 205th Street, then private property, then for a short portion under Van Cortland Avenue. West of Norwood–205th Street is a diamond crossover which allows trains that originate/terminate at the station to reach the correct track. A center track then forms, which leads to the Grand Concourse yard. The line then curves south at Mosholu Parkway to Grand Concourse, from which it derives its name, at 206th Street. Two tracks from the Grand Concourse yard arrive between the two revenue tracks with a trio of diamond crossovers between all four of them before entering Bedford Park Boulevard. This is where the local/express split begins, with the local tracks coming from the yard and the express tracks coming from Norwood. Contrary to standard practice, the local tracks are in the center and the express tracks are on the outside.
South of this station are diamond crossovers between the two center tracks, allowing originating and terminating local trains to reach the correct track so that they would not need to use the switches north of the station to relay. After this, each of the four tracks cross over one another to form the regular local-outer/express-inner configuration; there are another trio of diamond crossovers between all four tracks before the line enters Kingsbridge Road. The line then continues south along Grand Concourse. Due to the terrain, the vicinity of 174th–175th Street station is uniquely built both underground and over 175th Street. The line curves west before 161st Street–Yankee Stadium station and passes under the Harlem River into Manhattan via the Grand Concourse Tunnel. There is one more stop, 155th Street, before the line curves south on Saint Nicholas Avenue and joins the IND Eighth Avenue Line at the lower level of 145th Street station.
IND Queens Boulevard Line between Kew Gardens-Union Turnpike and Briarwood
G train extension to and from 18th Avenue station
DeKalb Avenue Junction
BMT Nassau Street Line
BMT Broadway Line between the 60th Street Tunnel and 57th Street–7th Avenue station
This underground station, opened on July 10, 1919, has four tracks and two island platforms. Just past the north end of the platforms, N, R, and W trains ramp down to a lower level and turn sharp east under 60th Street to 5th Avenue-59th Street, Lexington Avenue-59th Street, and then pass under the East River into Queens; Q trains stay on the upper level as they diverge directly north to the BMT 63rd Street Line and then the Second Avenue Subway to the Bronx.