service to Chambers Street, on June 24, 1950, was discontinued. All express trains began running to 57th Street on May 2, 1957. On October 24, 1957, late night service was replaced by locals to Chambers Street, running via the tunnel in both directions, and terminating at Coney Island–Stillwell Avenue. Express service was eliminated during middays, being replaced by locals extended to Coney Island on May 28, 1959. At this time all locals to Chambers Street began running via the tunnel in both directions. | R10–R38 rollsigns Letters began appearing in the summer of 1961, when R27 subway cars began running on the line. Express trains were given the label of T, and the locals were given the label of TT, in accordance with the Independent Subway System's old system labeling express trains with single letters and local trains with double letters. On January 1, 1961, rush hour T expresses began running to Astoria–Ditmars Boulevard in along the BMT Astoria Line in Queens, and until April 2, 1962 so did Saturday service. TT local service on January 1 began running between Bay Parkway and Chambers Street. During middays, local service only ran between Coney Island and Chambers Street. After April 2, 1962, T service began running to 57th Street during evenings and Saturdays; on nights and Sundays TT shuttle service ran to 36th Street. On May 2, 1962, T trains ceased stopping at 49th Street. Post-Chrystie Street Connection The T was discontinued on November 26, 1967, after the Chrystie Street Connection opened. This connection linked the new express tracks of the IND Sixth Avenue Line to the Manhattan Bridge, allowing for increased subway service between Brooklyn and Midtown Manhattan. As a consequence, the connection between the Nassau Street Line and the Manhattan Bridge was severed, ending the Nassau Street Loop in Lower Manahttan. The BB, a Sixth Avenue Line service which formerly operated solely in Manhattan, was now extended to Brooklyn via the Manhattan Bridge, running along the BMT Fourth Avenue Line and BMT West End Line to Coney Island. This new B service replaced T and TT service into Manhattan. However, late-night and Sunday shuttle service between Coney Island and 36th Street was still labeled TT. The new color scheme for subway routes introduced that day included a blue TT bullet. On July 1, 1968, the TT designation was discontinued entirely with late-night and Sunday shuttle service labeled B instead.