IRT withdrew from the agreement a month later, citing that it was inappropriate to enter such an agreement at that time. Thereafter, the PSC instead turned its attention back to the Main Street subway extension. Even after the Main Street station opened in 1928, efforts to extend the line past Flushing persisted. In 1928, the New York City Board of Transportation (BOT) proposed allowing IRT trains to build a connection to use the Whitestone Branch, but the IRT did not accept the offer since this would entail upgrading railroad crossings and the single-tracked line. Subsequently, the LIRR abandoned the branch in 1932. As part of the 1929 IND Second System plan, the Flushing Line would have had branches to College Point and Bayside east of Main Street. That plan was revived in 1939. The BOT kept proposing an extension of the Flushing Line past Main Street until 1945, when World War II ended and new budgets did not allow for a Flushing extension. Since then, several New York City Transit Authority proposals for an eastward extension have all failed. Service curtailments and slight improvements Second Avenue Line service, including the connection across the Queensboro Bridge, ended June 13, 1942, and free transfers to the IRT Third Avenue Line were offered at Grand Central. These transfers were valid until May 12, 1955, when Third Avenue Line service ended. On October 17, 1949, the joint BMT/IRT service arrangement ended. The Flushing Line became the responsibility of IRT. The Astoria Line had its platforms shaved back, and became BMT-only. Because of this, routes through the then eight-track Queensboro Plaza station were consolidated and the northern half of the structure was later torn down. Evidence of where the torn-down platforms were, as well as the trackways that approached this area, can still be seen in the ironwork at the station. During the joint service period, the elevated stations on the Astoria and Flushing Lines were only able to fit nine 51-foot-long BMT elevated or IRT cars, the rough equivalent of seven 67-foot-long BMT subway cars. After the BMT/IRT dual services ended in 1949, the New York City Board of Transportation announced that the Flushing Line platforms would be lengthened to 11 IRT car lengths, and the Astoria Line platforms extended to 9 BMT car lengths. The project, to start in 1950, would cost $3.85 million. Identification of Trains and Routing Automatically (IDENTRA) was implemented