Most of New York’s subway system still relies on antiquated technology, known as block signaling, to coordinate the movement of trains. A modern system, known as communications-based train control, or C.B.T.C., is more dependable and exact, making it possible to reduce the amount of space between trains. A computerized signal system like C.B.T.C. is also safer because trains can be stopped automatically. New York’s quest to install the new system began in 1991... More than 25 years later, the authority has little to show for its effort to install modern signals. The L line began using computerized signals in 2009 after about a decade of work. A second line, the No. 7, should have received new signals last year, but the project was delayed until the end of this year.
The process is complicated. It requires installing transponders every 500 feet on the tracks, along with radios and zone controllers, and buying new trains or upgrading them with onboard computers, radios and speed sensors. The authority also had to develop a design and software that was tailored to New York’s subway. Over the years, the authority has kept pushing back the timeline for replacing signals. In 1997, officials said that every line would be computerized by this year. By 2005, they had pushed the deadline to 2045, and now even that target seems unrealistic. Upgrading the signals is expensive, but an even bigger challenge is scheduling work on such a vast system where ridership is always high, even on weekends... (In London) The rollout of modern signals on four lines has significantly reduced delays, making travel across this huge city of nearly nine million people more efficient. This month, the Victoria line will reach a peak of 36 trains per hour — compared with 27 trains per hour a decade ago, and among the highest rates in Europe. In New York, the Lexington Avenue line, the nation’s most crowded subway route, runs a peak of 29 trains per hour.