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 . A Division numbers 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 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. Additionally, it appears on the rollsigns of some trains as a green 8, likely for the same reason as the two digit numbers. 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 B Division letters Trains of the B Division use single letters of the English alphabet. These service letters are unused, but some have been used or proposed for services at various points in time: 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