Nassau Street Loop

The Nassau Street Loop, also called the Nassau Loop, was a service pattern of the Brooklyn–Manhattan Transit Corporation (BMT) inaugurated in 1931 when the BMT Nassau Street Line was completed, providing a physical link that allowed a train to originate in Brooklyn, run through lower Manhattan and return to Brooklyn without having to terminate and reverse the direction of the train. Nassau Loop services have not been able to operate since 1967, when the Loop line's connection to the Manhattan Bridge was severed.

The Centre Street Loop was a similar service proposal that was never completed. Together, they are referred to as the BMT Brooklyn Loops.

Trains using the Nassau Street Loop originated on the services to Coney Island and Bay Ridge. All the services merged at DeKalb Avenue station, and then split into four tracks over the Manhattan Bridge and two through the Montague Street Tunnel. Before the Nassau Street Line opened, the following service patterns were used:

The Nassau Street Line was completed on May 30, 1931, and a fourth service pattern was added: the Nassau Street Loop. Trains could enter Manhattan along the south bridge tracks or through the tunnel and return via the other.

The Nassau Street Loop opened with two regular rush hour services, Monday– Saturday:

In 1934 two "Bankers' Specials" were added. Unlike the two existing regular services, these were special runs, one express service from the Brighton Line and another express from the Fourth Avenue Line. They operated during morning rush-hour only.

In 1950, Nassau Loop service reached its greatest extent when both Bankers' Specials added evening rush-hour service.

On May 28, 1959, in a massive round of service cuts known locally as the "May Massacre," Culver–Nassau service was eliminated entirely. The West End–Nassau trains ceased using the Manhattan Bridge part of the loop, turning at Chambers Street instead.

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