IRT A Division Edit
IRT White Plains Road Line north of East 180th Street and south of Jackson AvenueEdit
142nd Street JunctionEdit
North of the three-track/two-side platformed 135th Street station on the IRT Lenox Avenue Line in Manhattan is a two-level flying junction where trains can either continue on Lenox Avenue to 145th Street and 148th Street – Lenox Terminal stations or diverge northeast to the IRT White Plains Road Line in the Bronx. Also, there isn't a diamond crossover between the two tracks until just to the east of 148th Street – Lenox Terminal station; lastly, 145th Street is a full-length 510 feet IRT A Division station instead of half-length (255 feet).
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 southbound express trains to change to the local track and a corresponding switch on the lower level allows trains on the northbound local track to change to the express one.
The IRT Lexington Avenue Line between the Bronx and 116th StreetEdit
IND/BMT B Division Edit
Just at the south end of 145th Street station on the IND Eighth Avenue Line in Manhattan, the track work is quite complex. On the upper level, two tracks form between the local and express tracks in each direction; the express tracks end at bumper blocks at just under 141st Street.
On the lower level just at the south end of 145th Street station 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, as well as allowing express trains to originate/terminate at the station if necessary.
After the upper level express tracks end, the local tracks rising from the lower level merges with those on the upper level; while the express tracks rising from the lower level feed the rest of the IND Eighth Avenue Line express tracks, with diamond crossovers between those tracks and the aforementioned middle tracks in each direction, just before the line is shorten to six tracks and enters 135th Street station. The express trains use the innermost pair of tracks and the locals use the outermost tracks. The middle tracks, at this point, are lay-up tracks and not normally used by trains in passenger service. These tracks then end just north of 125th Street station, where they merge with either the express or local tracks; then there are diamond crossovers and switches between all remaining tracks just before the line enters 125th Street station.
This entire section of the IND Eighth Avenue Line, between 145th Street and 125th Street stations, is nicknamed "Homeball Alley" due to the large amount of switches, signals, splits, diverges, and merges in the area.
South of 59th Street – Columbus Circle station on the IND Eighth Avenue LineEditSouth 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. Downtown Eighth Avenue trains are never held outside north of the station by a downtown Sixth Avenue train. Downtown Sixth Avenue trains are delayed inside the tunnel to let one proceed first before the other can continue behind. All uptown trains may still be delayed from time to time, however.
IND Grand Concourse LineEdit
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 switches and 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/terminating local trains to reach the correct track and without the need to use the switches north of the station to relay local trains. After this, each of the four tracks cross over one another to form the regular local-outer/express-inner configuration before entering 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, then the line curves south on Saint Nicholas Avenue, just before it joins the IND Eighth Avenue Line at the lower level of 145th Street station.