An R62A-class car operating on the 42nd Street Shuttle erroneously shows an upside down 11 sign instead of the usual gray-backgrounded S for shuttles. The purple color currently corresponds to the IRT Flushing Line.
An R32 train erroneously displaying a P sign instead of the proper J
An R32 rollsign erroneously displaying the JFK Express logo. This service was used from September 1978 to April 1990 for limited super-express service to JFK Airport
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 June 2019[update].
8 was last used for the Bronx portion of the Third Avenue El from 1967 to 1973 (when it was demolished). Previously it was used by the IRT to designate their route that used the Astoria Line, which was originally jointly operated with the BMT prior to 1949.
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.
All of these two-digit bullets can be seen in R62A rollsigns.
B Division letters
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 is the internal route designator for the Rockaway Park Shuttle. It was used publicly until 1993, when the public route emblem was changed to S. Since then, the shuttle has only been referred to as H in internal documents. It 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.
I has never been used due to its visual similarity to the number 1.
X was originally proposed as a route from 21st Street to the World Trade Center (via the IND Sixth Avenue Line), but the route never surfaced.X is used as a placeholder for routes 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.