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The Complicated Progression of CBTC

MTA is scheduled to complete CBTC installation on the 7 Line in 2017

If all goes according to plan, the MTA will complete installation of Communications Based Train Control (CBTC) on the 7 Line this year. It will have taken seven years to complete and will be the second of the 22 subway lines to be fully upgraded. Installation on the first line to receive a CBTC installation, the L Line, took ten years. In a recent speech Governor Cuomo lamented that at this rate it will take 40 years to upgrade the entire system. In a 2014 report, the Regional Planning Association (RPA) calculated it would actually take more like 50 years and proposed a fast track that would “only” take 30 to 35.

Why is CBTC taking so long?

First, a CBTC primer

CBTC is a computer-based signaling system that allows trains to run faster and closer together than the existing fixed block system, thus allowing more trains to run. The system is more reliable, more flexible, more resilient to climate changes. It is a simpler system overall and therefore costs less and is easier to maintain. You can learn about CBTC in two great explainer videos, one from the RPA here,  and one from the MTA here.

NYC subway CBTC installation can get tripped up in any number of ways.

Other cities around the world have installed CBTC. In its 2014 study, the RPA highlighted four systems for comparison. London, for example, has a subway system of comparable age and size to the MTA. Almost 70 percent of the system has CBTC installed or in the planning stage. Paris too, with a system that began operation in 1900, has modernized 3 of its 13 lines with three more underway or in development. So why can’t the MTA keep up?

System Complexity

The initial installation on the L line might have taken ten years because it needed to incorporate some learning curve. With seven years of installation, the 7 train took comparatively less time, considering the line has fewer stations but both express and local tracks. But the 7 and the L lines are the least complicated in the system without line branches or splits so the challenges will only increase from here.

But even for its complexity, London’s system does not have express tracks like the MTA. It has installed CBTC on four of its lines and is working on four more, which are not necessarily a sure thing. In an article in Next City, Stephen Smith suggests system complexity might be the downfall of CBTC completion in London. Smith points out that while London has had much success installing CBTC on its simpler lines, “London’s more complex lines — the Circle, District, Hammersmith & City and Metropolitan sub-surface (rather than deep tube) lines, which have more junctions and connections between each other and the national rail network… have so far stymied the vendors who have tried to outfit them with CBTC, with two different signaling contracts canceled, likely owing mostly to the complexity of the job.” While, the RPA points out that the entire system does not need to be converted to CBTC to see benefits, it needs to at least be on trunk lines. The NYC subway is even more complicated than London’s and the MTA has barely made a dent in CBTC installation.

In addition to being arguably the most complex system in the world, many of the MTA’s lines are beyond maximum capacity. In 2014, 15 out of 20 lines were at peak track capacity, ten of which were at track and passenger carrying capacity. The Second Avenue subway has reduced that number of maxed out lines by one.

After the L and the 7 Lines, the MTA plans to tackle the Queens Blvd Line, which will be a better indicator of how system complexity impacts the CBTC installation system wide.


The completion of any project, including of course CBTC, is also tied to money. In 2014, the RPA estimated full implementation of CBTC on the subway would cost about $20 billion in 2014 dollars over a 35-year period. This is assuming the MTA adopts the accelerated schedule of upgrading 21 track-miles annually instead of the MTA’s stated goal of 16.

Money is as complex an issue as the system itself. While recent reports from the Independent Budget Office, which called out the MTA for increased delays to signal upgrades and criticizes the swelling costs of current projects, and the CBC also, which criticized the MTA recently for underinvesting in priority needs like signals, those under investments do not necessarily indicate a lack a priority. A recent New York Times article sums up the conflict:

“The problem has been one of simple math and competing interests. The money must be spread among all of the M.T.A.’s agencies, including two commuter railroads, nine bridges and tunnels, a bus system and the largest subway network in the country. Most importantly, say transit advocates and experts, the money spent has never been enough, leading to the current crisis.”

In that article, Veronica Vanterpool, an authority board member who heads the advocacy group Tri-State Transportation Campaign, defended the MTA saying, “The level of investment we’ve been making every five years is inadequate. The M.T.A. puts out a capital program with a price tag based on what is politically feasible, instead of what the system truly needs.”


Possibly the most limiting factor to any improvements in the system, though, more than complexity and money, is the very thing that makes the New York City subway so unique: 24-hour service. While other systems shut down in the evenings for at least a few hours, the MTA does not ever close to allow for daily maintenance.

In order to install CBTC more quickly and with minimal service disruptions, for example, London Underground took advantage of overnight hours and administered full weekend closures.

Not only does it never shut down, when the MTA must close a station or a line, it endures the endless wrath of its customers. Continuous weekend shutdowns of the 7 line, for example, have infuriated those who depend on it. Anticipating similar backlash, the MTA has been making a long term effort to prepare riders for the future L train shutdown.

Even if the MTA could iron out the kinks in its complex system and had endless money, when could it actually do the work? There is only one answer and it’s a hard one for riders to hear.

Will the MTA Genius Transit Challenge help the MTA untie this knot? Read about the Genius Transit Challenge here.