R39 was the proposed contract number for lightweight subway/elevated New York City Subway cars. They were intended to replace old equipment running on the BMT Myrtle Avenue Line in Brooklyn and the IRT Third Avenue Line in The Bronx.
The cars, which were to have been built to IRT dimensions, were to be a smaller, lighter-weight version of the R38 car, and were to have been ordered in the late 1960s or early 1970s. Portions of the elevated structures of the lines for which these cars were intended were built in the late 19th century and had never been strengthened to accommodate the standard subway cars used on all other lines.
The Budd Company used a possible outline of this car as U.S. Patent 3,151,538.
The cars were never ordered as it was determined that it would be possible to discontinue and dismantle the lines where the R39 would be used. The Myrtle Avenue Line south of the junction with the BMT Jamaica Line was discontinued in 1969, and the remaining Third Avenue Line in 1973.