the Lexington Avenue Line station. The construction of the narrow island platform station required building two new trackways extending east under 42nd Street. The two-track layout was expected to provide ample capacity for the shuttle. On August 1, 1918, the Dual System's "H system" was put into service, with through trains over the IRT Lexington Avenue Line and IRT Broadway–Seventh Avenue Line, and only shuttle trains under 42nd Street. The station was not ready in time, and therefore wooden flooring was temporarily laid over sections of the trackways at Times Square and Grand Central. The shuttle was heavily used, and the crowding conditions were so bad that the shuttle was ordered closed the next day by the Public Service Commission. The new, unused trackways of the planned station were covered with flooring and turned into a passageway between the Shuttle and Lexington Avenue stations. The shuttle reopened on September 28, 1918, with improved passageways and platforms. Track 2 at the Grand Central station was covered over by a wooden platform. A New York Times columnist later said that former southbound express track 2 was still usable for the first few hours of the shuttle's operation, but the wooden platform was placed over that track later the same day to allow shuttles to use former northbound express track 3, due to high demand for the shuttles on the former local tracks, numbered 1 and 4. On the walls of the stations, black bands (at Times Square) and green bands (at Grand Central) were painted to guide passengers to the shuttle platforms. The shuttle was meant to be "temporary," and by 1922, there were proposals for the shuttle to be replaced by a moving sidewalk. On March 14, 1927, the extension of the IRT Flushing Line from Fifth Avenue to Times Square under 41st Street was completed and opened for operation. The extension was expected to significantly reduce overcrowding on the shuttle, and on its first night of operation, it reduced shuttle ridership by 50%. Crowding was expected to be reduced further as riders became familiar with the extension. In 1921, of the 100,000 daily shuttle riders, 25,000 transferred to the Flushing Line (then called the Queensboro subway). Originally, plans for the Flushing Line called for the use of two of the four tracks between Times Square and Grand Central for the new line, and the other two for shuttle service. Proposed