A timer, counting up, is started as soon as the train passes a certain point and will clear the signal ahead as soon as the predefined time elapsed.

"One-shot timers", on the other hand, are found at sharp curves, and are named because the operator only has one chance to pass the signal within the speed limit.

[14] Wheel detectors prevent train operators from running slowly at the beginning of a grade timing segment and then increasing the speed beyond the allowable limit without being tripped.

[18] As of 2017[update], some of the oldest block signals in the system were 80 years old, and they broke down frequently, causing more delays and prompting the MTA to declare a state of emergency for the subway in 2017.

[23][18] In summer 2018, New York City Transit president Andy Byford created the SPEED Unit to reduce delays by modifying operating and service practices.

[6] The deployment of ATS-A involved upgrading signals to be compatible for future CBTC retrofitting, as well as consolidating operations from 23 different master towers into the Rail Control Center.

However, the MTA stated that due to high customer demand for train arrival displays, it would use a combination of CBTC and a new system, named the "Integrated Service Information and Management" (abbreviated ISIM-B).

The simpler ISIM-B system, started in 2011, would essentially combine all of the data from track circuits and unify them into digital databases; the only upgrades that were needed were to be performed on signal towers.

The CBTC Zone Controller functions then as an overlay which only provides safe separation of trains and cannot do so without interaction from the Wayside (Legacy) Signaling system.

The chairman of the Board of Transportation, Sidney H. Bingham, in 1954, first proposed a conveyor belt-like system for the shuttle line,[57][58] but the plan was canceled due to its high cost.

[59][60] Subsequently, in 1958, the newly formed New York City Transit Authority (NYCTA) started studying the feasibility of automatically operated trains which did not have motormen.

The bulk of the money, between $250,000 and $300,000, was contributed by the two companies, which paid for installation, maintenance and technological oversight of the automation process, including signaling.

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.

[78] In 1978, senior NYCTA executive John de Roos said that the authority would consider running automated trains following the completion of the 63rd Street lines, which were then scheduled to be opened in 1984 or 1985.

The collision was a catalyst to a 1994 business case outlining arguments for automatic train operation (ATO) and CBTC, which led to the automation of the BMT Canarsie Line starting in the early 2000s.

The two lines with the initial installations of CBTC were both chosen because their respective tracks are relatively isolated from the rest of the subway system, and they have fewer junctions along the route.

[3] Also included in the Capital Program is the installation of automatic signals on the line to facilitate the movement of work trains between interlockings.

The remaining segment of the Flushing Line, between the Steinway Tunnel and 34th Street–Hudson Yards, began operating in CBTC service on November 26, 2018.

[95] The project was substantially completed on March 7, 2019, and full automatic train operation began in May 2019, allowing for the increase in service to 29 tph.

[98] As part of the 2015–2019 Capital Program, the section of the line between Church Avenue and West Eighth Street–New York Aquarium would receive CBTC.

[100]: 6  A consultant for the MTA predicted that the CBTC system could not be activated as planned in March 2021 because of a lack of immediate funding and a shortage of CBTC-equipped trains.

[120] In December 2022, the MTA announced that it would award a $368 million design–build contract to Crosstown Partners, a joint venture between Thales Group and TC Electric LLC.

[124] CBTC installation on the rest of the Fulton Street Line from Euclid Avenue to Ozone Park–Lefferts Boulevard was proposed as part of the MTA's 2025–2029 Capital Program.

[132]: 26 The 2015–2019 Capital Program was revised in April 2018 to fund the upgrade of negatively-polarized direct current cables and the replacement of segments of contact rail with low resistance contact rail along Lexington Avenue to improve power distribution and increase capacity and to upgrade negative cables along Queens Boulevard.

[109][132]: 26 In December 2021, it was announced that the Sixth Avenue Line between Broadway–Lafayette Street and Jay Street–MetroTech would receive CBTC; funding for this section is not provided in the 2020–2024 Capital Program.

[138] In June 2022, the MTA announced it planned to solicit a contract on switch replacement and interlocking work as part of the Sixth Avenue CBTC project in 2023.

[141] As part of the 2025–2029 Capital Program (announced in September 2024), the entirety of the Broadway, Rockaway, Nassau Street, and Astoria lines would be upgraded to CBTC.

[145] New York City Transit (NYCT) Chairman Andy Byford stated that he wanted to test ultra-wideband technology at the same time that more established systems, like CBTC, are being installed.

[147] In June 2021, the MTA Board approved the modification of two UWB proof of concept contracts with Thales and Siemens to establish interoperability between the two systems.

[149] On April 7, 2022, the MTA put out a Request for Information (RFI) looking for information on technology that would allow work trains to efficiently and safely operate on subway lines equipped with CBTC and enable to reduction or elimination of Auxiliary Wayside Signaling (AWS) trip-stops and other standard wayside signaling infrastructure.