improvements Throughout the history of the shuttle there have been proposals to improve service on the line and to extend the line both to the east and to the west. However, it is not feasible to extend the line in either direction, as the line is at the same level as the tracks of the Broadway–Seventh Avenue Line and those of the Lexington Avenue Line. There have been several proposals to replace the line with moving walkways or conveyor belts. In 1923, H.S. Putnam proposed to replace the shuttle with an endless moving platform system. There would have been three platforms with speeds of , and . The fastest platform was to have been installed with seats. Even though the plan was supported by the Chief Engineer of the New York City Rapid Transit Commission, it was not adopted. In 1930, Charles E. Smith, vice president of the New York, New Haven and Hartford Railroad, proposed allowing trains from the Broadway–Seventh Avenue and Lexington Avenue Lines to use the shuttle tracks for through service, as well as discontinuing shuttle service. This also was not carried out. On February 12, 1946, work began to double the width of the passageway connecting the shuttle platforms at Grand Central and the main mezzanine over the Lexington Avenue Line platforms. As part of the work, the wooden passenger walkway, which had an average width of was replaced by a wide passageway with concrete flooring. This walkway had been "temporary" when it was put into place in August 1918. The new -long passageway covered most of the trackways used by downtown trains of the Original Subway prior to 1918. The iron railings along the planked walkway were removed. The project cost $45,800 and was intended to ease congestion. As part of the project, the upper passageway was moved to within fare control to allow passengers to go between the subway mezzanine and the entrance to Grand Central Terminal at the shuttle without paying a fare. This was accomplished by moving the turnstiles at the eastern end of the passageway. In March, members of the Metallic Lathers Union Local 46 sought to halt construction on the project, which was 80 percent complete, as the union objected to having the work done by city employees who made less than union workers. The rebuilt passageway opened on March 18, 1946. On June 21, 1949, William Reid, the Chairman