The Bowling Green–South Ferry shuttle was a shuttle service of the New York City Subway system that operated between Bowling Green and the inner loop platform at South Ferry. It operated to provide South Ferry service for IRT Lexington Avenue Line riders during hours when the 5 service did not stop at South Ferry. Because the inner loop station that the shuttle used at the South Ferry station was on such a tight curve, there was no continuous platform; instead four openings in the tunnel wall led into the station. Four R12 cars that were used on the shuttle, 5703–5706, which were modified and equipped so that only the center door of each car would open at one of the open spaces.

The R12 was a New York City Subway car built by the American Car and Foundry Company in 1948. A total of 100 cars were built, arranged as single units. Two versions were manufactured: Westinghouse (WH)-powered cars and General Electric (GE)-powered cars.