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The New York City subway system has made strides in recent years in upgrading stations, subway cars and passengers’ experience. But in one crucial area – signaling - the subway system remains antiquated, relying primarily on century-old technology to keep trains running. While New York is in the early stages of converting to communications-based train control, the modern telecommunications system that many of the world’s metro systems rely on today, the pace of change has been slow. At the current rate, a full transformation wouldn’t occur for more than 50 years, putting the city decades behind its peers around the globe.

What are the consequences of going too slowly?

More delays, increased safety risk and an inefficient use of resources. Because the network relies on old technology, repairs and replacement parts are costly. As the system ages, that burden will only increase.

What is holding New York back?

Resources, certainly. While CBTC will save money in the long run, it requires a substantial upfront investment in new systems and equipment. Future capital plans need to significantly increase funding beyond current levels. Converting to CBTC also could be done sooner with modifications to procurement rules and more flexibility to work on the tracks throughout the day. These are hard decisions that involve changes to longstanding procedures, but could speed up other projects in addition to signal work.

This report will explain what CBTC is and how it works. It will discuss the status of CBTC in New York City’s subway system, and make recommendations to implement it more quickly and efficiently.

What is Communications-Based Train Control?

Today, the New York City subway relies on a central nervous system made up of 15,000 signal blocks, 3,500 mainline switches and 339,000 signal relays. These components, which have hardly changed since the subway opened in 1904, let train operators know when it is safe for them to move trains forward.

The type of signaling system used by New York’s subway, called fixed-block wayside signals, divides the subway tracks into blocks of around 1,000 feet and creates a buffer of one or more additional trailing blocks to ensure safe separation of train traffic. The buffers limit the number of trains that can flow through the tracks at any one time.

The effects of these constraints have increased as subway ridership has grown. In the last 20 years, the number of passengers has climbed to its highest level since 1950, with more growth expected in the coming years. During peak periods, trains are forced to wait in stations while crowds of passengers exit and enter the cars, causing delays that ricochet through the system. The result is fewer trains running per hour. In off-peak hours, where ridership growth has been greater, it has become increasingly difficult to find adequate time to inspect, maintain and replace the signal blocks, switches, relays and automatic train stops without major effects on service. Dispatchers can only determine so much now about train location, and lack the precision and ability to centrally monitor and manage the entire system.

By contrast, CBTC combines the firepower of higher-speed computers and fiber-optic data communications to link tracks and vehicles into a seamless system. Computerized signal equipment installed along the tracks and on subway trains establishes precise knowledge about the location and speed of each vehicle, making it possible to centrally monitor and respond rapidly as conditions change.