The 42nd Street section of the line connected Broadway at Times Square, on the west, to Park Avenue at Grand Central Terminal, on the east.

[20] 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.

[28] On June 21, 1949, William Reid, the Chairman of the New York City Board of Transportation, announced that his capital budget request for 1950 would include $3.5 million to improve the shuttle for the first time since it was created.

[29] On October 28, 1953, the Transport Workers Union (TWU) asserted that it was impossible for its members to follow the schedule of the shuttle, which called for a train every two minutes during rush hours.

Its president, Michael Quill, said that if the New York City Transit Authority took action against train crews skipping scheduled runs, there would be unrest among the TWU's members.

[33] Even though New York City Transit Authority (NYCTA) and the Board of Estimate approved the plan it was not completed due to union opposition and high cost.

[11]: 13 On April 21, 1953, Board of Transportation Chairman Sidney H. Bingham, announced that the installation of the conveyor would cost $3.8 million and could be completed in 18 months after funding was budgeted for the project.

[34] On October 19, 1954, the single bid for the project was submitted by Passenger Belt Conveyors, which was a subsidiary formed the previous month by Stephens–Adamson Corporation and Goodyear Tire.

In May 1955, it was announced that the project was tabled for discussion for August 25 of that year at the request of City Controller Lawrence Gerosa, who considered the plan to be dangerous.

[38] On September 15, 1955, the Chairman of the New York City Transit Authority, which had taken over operations of the Board of Transportation in June 1953, said that the allocation of funds for the project was questionable.

[40] On August 16, 1954, a project to replace 1,000 incandescent bulbs with 2,200 feet (670 m) of new fluorescent lighting at Grand Central platform was completed.

The project would cost $1 million, and Patterson said that automating the shuttle would save $150,000 annually by reducing 25 train operators and conductors.

The automation of the shuttle was opposed by the president of the Transport Workers Union, Michael J. Quill, who pledged to fight the project and called the device "insane".

[48] A June 1961 report from the New York City Transit Authority (NYCTA) mentioned the automatic train was planned to be placed into service that November.

The experiment was intended to produce a smoother and more comfortable ride for commuters, in addition to lessening the effect of moisture and erosion.

[61] A severe fire at the Grand Central station on April 21, 1964, destroyed the demonstration train and resulted in the subsequent restoration of manual operations.

The entire project cost $419,000 and included the construction of a new mezzanine at Grand Central and the replacement of the wooden platform at Times Square with a new concrete one of 300 feet (91 m).

[67] In 1978, the United States Department of Transportation undertook a study to analyze and determine the feasibility of installing an Accelerating Walkway System in an urban environment.

[70] The shuttle ran at all times until September 10, 1995, when night service was discontinued in order to avoid raising fares, meaning that late-night passengers had to use the 7 train.

The elimination of late night service was part of a larger plan to reduce spending in order to avert a fare increase, which Governor George Pataki and Mayor Rudy Giuliani had pressured the Metropolitan Transportation Authority (MTA) to avoid.

[75] In 1998, MTA officials announced that the Times Square station would be renovated and that the entire complex would become compliant with the Americans with Disabilities Act of 1990 (ADA).

[77][78] In 2014 and 2015, the MTA commissioned WSP to undertake constructibility and feasibility studies to increase capacity on the shuttle and to make it ADA-accessible.

NYCT called for a plan that would include a wider center platform to accommodate two six-car trains to the east of the existing station.

NYCT then asked WSP to engage in a study, TO-3, to look into eliminating all platform edge columns while keeping the station open with minimal impacts.

[87] On November 8, 2019, the MTA solicited bids for a consultant to manage, oversee, and coordinate work on construction projects taking place in the subway system between Times Square and Grand Central, in order to improve customer communication, minimize inconveniences, and to reduce the length and cost of these projects by bundling work.

[91] However, on that date, New York City Transit issued a General Order that called for a complete shutdown of the line until December 31, 2020.

[94] The closure of the shuttle allowed the contractor to fix an unexpected tunnel settlement condition at Times Square, which would have otherwise delayed the project by three to four months.

The space currently used by passengers heading to and from the 43rd Street exit or to and from trains on track 4 will be placed outside of fare control for this new entrance.

A new fare control area was to be constructed at the west end of the passageway, leading to a new entrance on the north side of 42nd Street between Broadway and Sixth Avenue.

The passageway was to be used for a free transfer to the IND Sixth Avenue Line's 42nd Street–Bryant Park station, allowing passengers access to the B, D, F, and M trains.