The NX designation was used for a rush hour peak-direction "super-express" service along the express tracks of the Sea Beach Line, beginning at Brighton Beach on the BMT Brighton Line, running through Coney Island, and then following the N route to 57th Street–Seventh Avenue. This short-lived service began on November 27, 1967 (when the Chrystie Street Connection opened) and ended April 12, 1968 due to low ridership. Starting on Monday, April 15, 1968, the five NX trips instead ran as N trips.