In the 40 or so years after the opening of the Chrystie Street Connection, a series of service changes caused by construction work led to service patterns temporarily mimicking those of the original T and TT services. From April 26, 1986 to December 11, 1988, the northern tracks of the Manhattan Bridge, leading to the Sixth Avenue Line, closed for repairs, akin to the conditions of the subway prior to the opening of the Chrystie Street Connection. During this time, the T's old service pattern was almost exactly recreated, with B service running via Broadway Express from Coney Island to Astoria–Ditmars Boulevard during rush hours, and during middays, evenings and weekends to Queensboro Plaza. The TT's route via the BMT Nassau Street Line was replicated in 1987, when the M was rerouted from the Brighton Line to the West End Line running to Bay Parkway. The M ran on the BMT Nassau Street and West End Lines on weekdays until June 25, 2010. The Manhattan Bridge's north side tracks closed for repairs again on July 22, 2001; B service in Brooklyn via the Sixth Avenue Line was replaced by the new service, running via Broadway express to Astoria-Ditmars Boulevard, essentially recreating the T route once again. This lasted until February 22, 2004, when, following the completion of repairs to the Manhattan Bridge, the was rerouted over the West End Line, providing full-time service via Sixth Avenue Express, which continues today. The T bullet appeared on R32 rollsigns as a black letter on a white circle. The T was programmed into R44 and R46 side signs as a West End route, with various Broadway, Sixth Avenue and Nassau Street designations. Planned Second Avenue Subway service Designation During planning for the Second Avenue Subway in the early 2000s, the MTA decided to designate the line's future full-length service with the letter T, in part because: The letters O and I are too easily confused with the digits 0 and 1, respectively. The letter K was used until the late 1980s to denote services on the IND Eighth Avenue Line, and earlier on the BMT Jamaica Line, and thus is not preferred. The letter V was in use at the time (and until 2010) to denote services on the IND Sixth Avenue Line and IND Queens Boulevard Line. H is the Rockaway Park Shuttle's internal route designator. The letters P, U and Y