Few terms provoke as much dismay among subway riders as a signal problem. When just one small link in a chain of electrical connections, some nearly a half-century old, breaks down, MBTA commuters are often in for a long delay.
Now, though, the Massachusetts Bay Transportation Authority is boldly promising that signal problems, which account for about one-third of subway delays, will fall sharply with the installation of a new system on the Red and Orange lines.
On Monday, the T’s management board awarded a $218 million contract to Barletta Heavy Division to install the new system by 2021 on the Red Line, and 2022 on the Orange Line. The new system, T officials have said, could reduce signal failures by 50 to 70 percent.
The contract is a key element of a nearly $2 billion investment in the two lines that also includes hundreds of new subway cars to replace an aging fleet and renovations of major maintenance facilities. MBTA officials say that once the new cars and signal system are in place by the mid-2020s, they can run more frequent service with far fewer delays on the two lines.
“This was one of the main pieces of the pie for us to deliver in the next several years,” said MBTA general manager Luis Ramirez. “And this is also the real evidence of the full modernization we’re trying to do with the Red and Orange lines.”
Passengers may see signals as only a traffic light for trains. But the signal system includes a sprawling network of sensors and cables that determine when trains can proceed — and when they cannot.
On the Red and Orange lines, the system works by blocking off portions of track, allowing only one train at a time on each portion. The system also detects any obstructions or other issues with the tracks.
Even when a signal trips erroneously, the system requires trains to travel slowly if they bypass it.
The existing system dates to the 1970s and is controlled by analog components with dials that must be adjusted by T workers when they want to change a train’s top speed in a given area.
It will be replaced by a digital system that can be controlled remotely.
One of the biggest benefits of the new system is additional information about track issues. Today, if a piece of rail equipment is not properly functioning, a signal will turn red and require trains to follow protocol. But to find the cause of that red signal requires workers to inspect the rails manually, sometimes going screw by screw, before they can find the issue.
Last year, for example, workers searched a section of the Red Line for hours before realizing that tiny particles of metal had accrued inside insulation between two sections of track, enough to create a short circuit that turned the signal to red.
The new system, by contrast, will provide much greater specificity about where a track problem originated, allowing workers to address it more quickly.
“They’ll be able to be told by the equipment, ‘This is your piece of equipment that’s got a fault to it,’ so they can repair it,” said MBTA chief engineer Erik Stoothoff.
The new system will also allow workers to let trains travel at eight different speeds, compared to five today. And eventually the T will be able to run trains closer together in some areas. The new system will also be easier to maintain because the equipment is more modern.
The 152 new Orange Line cars, meanwhile, will be slowly introduced into service starting later this year, running through 2022, while 252 new Red Line cars are expected to be fully in service in 2023.
Officials have promised that once the projects are complete, the Red Line will run trains every three minutes during rush hour, and every 4½ minutes on the Orange Line. On-time performance will increase to more than 95 percent, they said, compared to roughly 90 percent today.
But there will be growing pains. Parts of the two lines will be shut down for at least 26 weekends over the course of the project to allow for the signal work.
MBTA deputy general manager Jeff Gonneville said the new system could form the basis for additional train control technology, such as a system called automatic train operation that speeds service by automating stopping and acceleration at stations.
The T is considering that technology for the Red and Orange lines, but has not yet issued a contract to install it.
The MBTA is also replacing signals on the Green Line, starting with the D branch, which is undergoing major track replacement work. The agency will also soon launch a study of how to improve signals on the Blue Line.