began in 1922. The tunnel was extended to Fifth Avenue on March 23, 1926, and Times Square on March 14, 1927. When Belmont modified the IRT Flushing Line to extend to Times Square and to Flushing, it was found that the loops could not be used for the extensions. The loops on the Queens side of the tunnel were obliterated in the wake of new construction. The loop on the Manhattan side, however, is intact and occupied by maintenance rooms, although the ceiling third rail still exists in the loop. The line from Times Square to Flushing was completed in 1928, when the station at Flushing opened. Since the tunnel ramps towards Queens were significantly steeper than normal IRT specifications, with a gradient of 4%, special rolling stock had to be procured for the Steinway Tunnel line. The "Steinway"-type subway car had the same dimensions as an ordinary subway cars of the IRT, but included modified gear boxes. Initially, twelve single-car consists were approved for the original shuttle. Because of additional construction to the route, another 126 cars were added to the fleet. The 50 "World's Fair"-type cars, used for the 1939 New York World's Fair, used the same type of gear boxes. With the 1948 introduction of four-motor subway cars of types R12 and R14, the need for a special drive was gone, as the Steinway Tunnel could now be driven by conventional railcars. In 1949, BMT services stopped operating on the Flushing Line east of Queensboro Plaza, and the IRT was assigned exclusive operation of the line. In subsequent years, the tubes of the Steinway Tunnel were difficult to maintain: they were prone to flooding, and the tube walls were much narrower than other tunnels in the subway system, with almost no clearance on each side of the train. After a train got stuck in the tunnel in 1971, a passenger died of a heart attack. A fire broke out on a train in the tunnel in 1973, killing one passenger and trapping over a thousand in the middle of the tunnel, after the collapse of an archway. In 1991, the tubes were flooded to after a water main broke on the Manhattan side. The next year, an electrical fire in the tunnel melted several feet of steel rail, although the tunnel's exhaust fans were working properly. After Hurricane Sandy-related storm surges flooded the tunnel in 2012, the