The New York City Subway currently uses various letters and numbers to designate the routes that trains use over the differing lines in the system. Along with the color corresponding to the route's trunk line, these form a unique identifier for the route, easing navigation through the complex system. Several service labels have either been phased out or never been used. This list covers the labels not used as of November 2016.
The A Division uses single-digit numbers for each route. Currently numbers 1 through 7 are in use.
0, while not used publicly, is used as the internal designation of the 42nd Street Shuttle.
8 has been used in the past for various routes, most recently the Bronx portion of the Third Avenue El, demolished in 1973.
9 was last used for skip-stop service on the IRT Broadway–Seventh Avenue Line from 1989 to 2005. Previously, it was used as the designator for the IRT Dyre Avenue Line shuttle between 1941 and 1966.
Two-digit numbers have never been used by the A Division, but have been seen on the current rollsigns of some trains, paired with colors used with other services. It is likely that these were assigned arbitrarily, for use if the MTA changed the additional rush hour express service designators from a "diamond" version of the regular number to a separate number.
Two-digit bullets include:
A green 10 for the IRT Lexington Avenue Line
A purple 11 for the IRT Flushing Line
A green 12 for the IRT Lexington Avenue Line
A red 13 for the IRT Broadway–Seventh Avenue Line
All of these two-digit bullets can be seen in R62A rollsigns.
Trains of the B Division use single letters of the English alphabet. These service letters are unused as of November 2016, but some have been used or proposed for services at various points in time:
H was last used publicly for a fare-free shuttle service in the Rockaways, started in November 2012 after damage caused by Hurricane Sandy rendered normal A train service in the area inoperable; this temporary service lasted until May 2013, when full A train service to the Rockaways was restored. Previously, it had been used for the Rockaway Park Shuttle until 1993, but is still used as its internal-only designator by NYC Transit.
I has never been used due to its visual similarity to the number 1.
K was last used as an Eighth Avenue Line local train (discontinued in 1988). Prior to that it was used for a 6th Avenue Line local service via the Chrystie Street Connection.
O has never been used due to its visual similarity to the number 0.
P (short for Penn Station) was planned for a nonstop between Sutphin Boulevard–Archer Ave (at the LIRR's Jamaica station) and 34th Street–Penn Station, continuing locally to 168th Street, via the BMT Archer Avenue Line, BMT Jamaica Line, Chrystie Street Connection, IND Sixth Avenue Line and IND Eighth Avenue Line (switching to the latter at West Fourth Street) in the 1990s. This would have been used during a threatened Amtrak strike that would have prevented LIRR trains from entering Penn Station. The letter has never actually been used, as it also sounds like the word "pee".
T was used for BMT West End Line services, but was quickly replaced by the expanded B service after services were reorganized following the opening of the Chrystie Street Connection. T is the planned label for the new Second Avenue Subway.
U has never been used, as it sounds like the word "you".
V was introduced in December 2001 for weekday local service on the IND Queens Boulevard Line and IND Sixth Avenue Line via 53rd Street, after the F train was shifted to the newly opened IND 63rd Street Line. V service was discontinued in June 2010 due to budgetary concerns, being replaced almost entirely by a rerouted M train.
X is allegedly used as a placeholder for subway lines under construction.
Y has never been used, as it sounds like the word "why".
The JFK Express's bullet, featuring an airplane symbol inside a turquoise circle, was used from 1978 until 1990.
Prior to May 1985, the B Division used two-letter combinations to indicate differing variations of similar services, but these were phased out in favor of single-letter designators. These former service names are covered in their corresponding current letters.
The letters H, K, and V can be seen on the rollsigns of the older subway cars, with colors paired to the last primary trunk line they were assigned to. The letters P, T, U, X and Y can also be seen on R32 side rollsigns as a black letter inside a white circle.
