The New York City Subway’s Canarsie Line was the first line in the system to use communications-based train control (CBTC).
The line carries the L service between Eighth Avenue in Manhattan and Canarsie–Rockaway Parkway in Brooklyn. Its modernization introduced automatic train supervision and moving-block signaling, allowing trains to be managed by continuous two-way communication rather than relying solely on fixed blocks.
The Canarsie Line became an important testing ground for CBTC because it is a relatively self-contained route. The technology helps reduce train spacing and can improve reliability, although service can still be disrupted by power, track, signal, or equipment problems.
This fact is sometimes confused with the Flushing Line, which also received CBTC and operates the 7 and <7> services. The Flushing Line was upgraded later; the Canarsie Line’s L service is the system’s pioneering CBTC route.