8 (New York City Subway service)
Astoria Line 
The 8 label was first used for the Astoria Line, which opened on February 1, 1917 as an extension of the Queensboro Line (now part of the Flushing line) from Queensboro Plaza. The Corona Line (now also part of the Flushing Line) had already been built as another branch from Queensboro Plaza; when the Astoria Line opened half the trains ran to each terminal. At the time, the Queensboro Line ended on the other side of the Steinway Tunnel at Grand Central.
Tracks opened over the Queensboro Bridge on July 23, 1917, allowing elevated trains of the IRT Second Avenue Line to operate to Queensborough Plaza and then over either the Astoria or Corona line. Once this link opened, all elevated trains went to Astoria, and all subway trains to Corona, but this was modified by 1923, with both divisions running on each line. On March 22, 1926, the Queensborough Line (and Astoria service) was extended west to Fifth Avenue, and it was completed west to Times Square on March 14, 1927.
BMT shuttles (coincidentally also labeled 8) began using the Astoria Line on April 8, 1923, with a transfer to the Broadway Line at Queensborough Plaza. This joint operation ended on October 17, 1949, and all IRT trains started operating to Flushing (where the Corona Line had been extended in 1928) and all BMT trains operated to Astoria. The numbers were only publicly used starting in 1948, so the public only knew the Astoria Line's IRT services as the 8 for about a year.
Third Avenue Line 
When the Chrystie Street Connection opened in late 1967, the TA assigned labels to all services. The only remaining IRT elevated line, the IRT Third Avenue Line in the Bronx, was too long to be a shuttle, so was assigned the number 8, unused since 1949. This service, running between 149th Street and Gun Hill Road, last ran on April 28, 1973, when the Third Avenue Line closed, and was replaced by the Bx55 bus route. The 8 bullet was only marked on maps and station signs, never on cars. Cars instead displayed SHUTTLE and the destination.
Present status 
See also 
- BMT 8, the BMT service that operated in tandem with this service until 1949
- Unused New York City Subway service labels
- "Dufunct Train Lines - nyc.transit | Google Groups". Groups-beta.google.com. Retrieved 2012-02-24.
- New Astoria Line Opened, New York Times February 2, 1917 page 14
- Subway Link over Queensboro Bridge, New York Times July 22, 1917 page 31
- Additional Subway Service to Borough of Queens, New York Times April 8, 1923 page RE1
- Fifth Av. Station of Subway Opened, New York Times March 23, 1926 page 29
- New Queens Subway Opened to Times Sq., New York Times March 15, 1927 page 1
- Direct Subway Runs to Flushing, Astoria, New York Times October 15, 1949 page 17
- Third Ave. El Reaches the End of Its Long, Blighted, Nostalgic Line, New York Times April 29, 1973 page 24