As part of negotiations between New York City, the Brooklyn Rapid Transit Company (BRT), and the Interborough Rapid Transit Company for the expansion of the city's transit network, the line was leased to a subsidiary of the BRT. The agreement, known as Contract 4 of the Dual Contracts, was signed on March 19, 1913. In 1912, during the Dual System negotiations, the construction of an extension of the Fourth Avenue subway from 43rd Street to 89th Street, just south of the 86th Street station, was recommended. The proposal was approved by the Board of Estimate on February 15, 1912. The PSC directed its chief engineer to create plans on June 14, 1912. The two contracts for the extension, Route 11B, were awarded on September 16, 1912, to the Degnon Construction Company for a combined $3.8 million (equivalent to $ million in ).