Hi-Tech Underground

Adapting Modern Train Controls to an Aging System

by Tom Stabile

Upgrading a 70-year-old signal system on the L subway line in Brooklyn and Manhattan would have been hard if the only goal was to keep it running smoothly.

But the goal of a $287 million project  nearing completion on the L, also known as the Canarsie Line, is to transform that old network into New York City Transit’s first foray into automated train controls.

Automation guides trains in newer transit systems around the world. Still, the task of adding such technology to an existing subway – no less one as old and complex as New York’s – was a giant effort.

“We’re the only ones to do it on such a large scale on an existing system,” says Cosema Crawford, chief engineer for New York City Transit.

The project entailed elements that are part of other bigger initiatives, such as installation of advanced interlockings, signal upgrades, and laying of fiber optic cable. CBTC adds an overlay of software and special controls that will allow computers to control all or parts of routes, allowing for closer train spacing, while also funneling train location data to the agency’s rail control center and eventually to passengers via information screens.

The system uses computer instrumentation on a train to measure speed and location, allowing it to coordinate with controllers along the trackway that account for track conditions – such as curvature, nearby work orders, and the location of other trains – in order to calculate a safe traveling speed. It also has the capability to override a red signal from the conventional system, and convert it to a flashing green, if it calculates that a train can travel forward at a safe speed, says Nabil Ghaly, program officer and chief signal engineer for New York City Transit’s department of capital program management, who has overseen the planning, installation, and commissioning of the new system.

Awarded in 1999 to a joint venture of Siemens, Union Switch, and Railworks, the effort is finishing several months behind schedule. By mid-winter, nearly all systems except for the tie-in to passenger information terminals were running.

It signals a major shift to a more efficient system, Ghaly says.

“It has a fundamental impact on the way we do business for operations, maintenance, and how we service for our customers,” he adds.

Installing the system was no easy task.

“There are a number of challenges,” Ghaly says. “The hardest is to implement such complicated systems on a railroad that operates 24-7 with minimal impact on our operations.”

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Still, bringing CBTC to the L train was in some ways easier than its eventual spread to the rest of the system, because it runs alone on a dedicated track, back and forth between Brooklyn’s northern neighborhoods and Manhattan’s 14th Street.

Bringing the technology to the rest of the system, which has various types of tracks, trains, and signals, is a major task.

“We have to migrate this technology to our lines in a way that minimizes changes to existing wayside signaling,” Ghaly says. “We’re going to do the branch lines first in the outer boroughs, so that when we come to Manhattan for the trunk lines, most trains will be equipped from prior steps.”

The next line to get the work, however, will be the system’s only other “captive” line, the Flushing or No. 7 line. The CBTC project, budgeted at more than $100 million, is set to start in June and finish next year on stations between the current terminus points in Queens and Times Square in Manhattan, Crawford says.

“It’s a very busy, three-track line,” she says. “It’s easier than the L because we use the middle track, but it is very difficult if you need to shut down all three tracks, and we will need to.”

Another upcoming project is a $135 million modernization to add relay-based interlockings on the A, C, and E lines at three Lower Manhattan stops to prepare for CBTC and the automatic train supervision system that transmits train data from interlockings to the rail control center.

The Culver line, or F train in Brooklyn, Manhattan, and Queens, is next up for CBTC in 2010, followed by the rest of the “letter” trains of the old IND and BMT lines. The “numbered” trains of the old IRT line are not getting CBTC in the near term, because their signal systems were modernized in recent years with conventional wayside equipment, Crawford says.

The task ahead is formidable but doable, says Jeff Levy, Railworks president.

“If you could shut the highway down and rebuild it, it would be great, but you have to do it a lane at a time, and that’s how they have to do CBTC,” he says. “Everything is done with a bigger goal of better communication and integration.”

And Ghaly says the future tasks will be somewhat easier in one respect – they will have a template.