Other lines have in the past been designated S; the label has also been used for temporary shuttles due to construction. Before 1986, all shuttles had the label SS, and S was reserved for 'special' services, including IND trains to Aqueduct Racetrack. The SS label was first applied in 1967, when all services were labeled due to the completion of the Chrystie Street Connection.
See HH for the old Court Street Shuttle and the later Rockaway Shuttle. See 3 for the old Third Avenue Shuttle in the Bronx (shown as SHUTTLE on rollsigns).
Former uses of the S or SS designation are as follows:
When the extension to 148th Street opened, the hours were extended to run all the time that the 3 didn't run (late evenings and late nights). Then between 1969 and 1972 it was folded into the 3, but continued to run as simply a shuttle at those times. Late night service last ran on the morning of September 10, 1995.
The 3 now runs at all times but late nights, but the shuttle survives Sunday mornings from 06:00 to 08:30, when the 3 only runs north of 135th Street.
The East 180th Street-Dyre Avenue Shuttle (also Dyre Avenue Shuttle) was established as a new subway service and full-time shuttle in 1941 between the former East 180th Street station of the New York, Westchester and Boston Railway and Dyre Avenue, which was the last station of the NYW&B within New York City. Passengers had to make a walking transfer between the Dyre Avenue Line and the IRT White Plains Road Line at East 180th Street as the two lines did not share a common station and there was no track connection between the lines.
In 1957 a flyover connection opened between the East 180th Street station of the White Plains Road Line and the Dyre Avenue Line, enabling through service by trains of the 2 from Manhattan to Dyre Avenue. At the same time, the former NYW&B station was closed and off-hours Dyre Avenue Shuttles rerouted to the White Plains Road Line station. These shuttles were initially labeled 2 like the full-time service but were later signed 3, a number used for IRT Broadway-Seventh Avenue Lineskip-stop service.
The off-hours Dyre Avenue shuttle still operates, but trains on the line are signed 3, the same as the through service that now serves the line.