Questions mount on slowed Green Line extension track, which T says ‘has always been narrow’

The year old Green Line extension is having track issues, so the train must travel slowly in certain spots.David L. Ryan/Globe Staff

The long-awaited, $2.3 billion Green Line extension, which opened last year to celebration from Somerville and Medford, has always had narrow tracks, the MBTA said Wednesday. But they have somehow dangerously narrowed more in recent months, forcing safety slowdowns, and the T isn’t saying why.

The T declined to explain why the project was built with narrow tracks or why such serious problems are happening so soon after it opened — at some points now, trains can only safely go 3 miles per hour — or who was responsible.

The oddness of the significant slowdown on the T’s newest stretch left just about everyone scratching their heads Wednesday, including the mayors of Boston, Somerville, and Medford; engineers; riders; and Governor Maura Healey.

Healey said the major question is “how these defects can be possible after only a year in service.”

”That’s the question [MBTA general manager Phillip] Eng and his team are asking,” Healey said in an interview, “in addition to fixing and conducting the inspections.”

Healey, a Democrat, also said she shares the public’s frustration with the slow zones on the Green Line, and noted that the extension was constructed and opened under the “prior administration” of Republican Charlie Baker.

MBTA spokesperson Joe Pesaturo, for his part, emphasized “the Green Line extension was constructed and opened under the previous administration,” and said the width between the rails on the tracks of the branch to Union Square, opened in March 2022, and Medford, opened in December, “has always been narrow.”

Only in the last three months, however, has the width between the rails become narrower in certain areas to the point that it is dangerous for trains to go full speed, he said.

As of Tuesday, 14 slow zones blanketed the Green Line extension, forcing trains to travel at 3 miles per hour for stretches that add up to a distance of more than a mile, a discouraging blow to riders who are already enduring reduced service.

The track problems are “puzzling,” one expert said, especially since the final branch to Medford opened so recently.

Rail width can narrow over time, said Pasi Lautala, the director of the rail transportation program at Michigan Tech Transportation Institute, but narrowing can be caused by rotting track parts that takes decades, and it’s usually an isolated incident, not widespread.

“You should not see those kinds of problems if everything was designed and built properly,” he said. “This sounds like something happened systematically when it was built that created this issue.”

Pesaturo said the T is working to determine the cause of “these aberrations in the track gauge.”

“GLX Constructors is responsible for addressing the defects, and they will continue to perform the necessary work,” he said, referring to the joint venture of companies that built the long-promised expansion.

“If we need to address anything with the GLX contractor about the quality of its work, we will do so,” he added.

A joint venture of Fluor Corp., a Fortune 500 company based in Irving, Texas; Balfour Beatty Infrastructure Inc., of Atlanta; Herzog Contracting Group, of St. Joseph, Mo.; and the Middlesex Corp. of Littleton built the Green Line extension. The companies didn’t respond Wednesday to requests for comment.

Until Wednesday, the MBTA and Healey had blamed disinvestment in the transit system and its old age for the widespread slow zones across the subway. Now, Eng, the general manager, is adding “past decisions” to that list, without providing specifics about which decisions caused the current troubles.

“Since becoming general manager, delivering safe, reliable, and improved service has been a priority,” he said in a statement. “To do that, we remain committed to addressing infrastructure problems that we have inherited caused by years of disinvestment and past decisions that have led us to this point in time.”

Jim Conroy, a spokesperson for Baker, promoted the former governor’s record on transit.

“The Baker-Polito administration is proud of their accomplishments at the MBTA which includes record investment in deferred maintenance, record investment in new track, signals and cars, and saving the long-promised Green Line Extension that was in danger of being cancelled,” Conroy said in a statement. “As it pertains to the fine points of track construction, the Baker-Polito administration defers to engineers and experts at the MBTA.”

Maria Hardiman, a spokesperson for the state agency that oversees safety matters at the MBTA, the Department of Public Utilities, said it is “currently investigating the narrow gauge defects and associated geometry reports that prompted the speed restrictions on the Green Line extension.”

Before the extension opened, the DPU, safety officials at the MBTA, and the Federal Transit Administration certified the project complied with relevant safety standards, Hardiman said.

A spokesperson for the FTA did not respond to a request for comment.

The subway system has been plagued by slow zones in recent years as the T has opted to slow down trains instead of making critical track repairs. Last summer, the FTA called the T out for that practice and ordered the agency to prioritize maintenance and improve service.

Since then, two reports have found that the T’s track department missed dangerous problems on vast swaths of the subway as recently as March because of inadequate training and inexperience, among other problems.

Mayors of Boston, Medford, and Somerville expressed concern Wednesday about the T’s newest line already showing problems.

Boston Mayor Michelle Wu said it’s important for such troubles to be disclosed publicly “before anything dangerous might have happened.”

“But this is a brand new line,” she told reporters. “We have a lot of work to do.”

Medford Mayor Breanna Lungo-Koehn said that she is concerned about future disruptions and “that there are wear and tear issues and we’re just a year out.”

In a statement, Somerville Mayor Katjana Ballantyne said she is concerned about the reliability of the system in the city and beyond.

“Massachusetts neglected the MBTA for decades, and we are learning that the consequences go beyond older infrastructure like the Red Line and Orange Line — even new systems and facilities like the GLX can be impacted when our public transit authority is chronically underfunded,” she said.

Laurel Ruma, who lives near the Green Line extension in Medford and served as a citizen representative during planning for the project, said she noticed the slow zones on Wednesday while she was traveling to her job in Cambridge and wondered whether she could get there faster by bus.

“Between the GLX Constructors and the MBTA, it’s clear that the proper oversight did not happen,” Ruma said.

One key lawmaker gave some slack to the governor and Eng, who started in April.

House Speaker Ronald Mariano said Healey and the MBTA’s new leadership should be given latitude to address problems, including the Green Line extension tracks, noting that they “were put down long before these folks were hired by the T.”

”It’s a sign of how big the problem is and how important it is that we get on and fix it. I think they’re going to need all our help,” he said.

But the Quincy Democrat did not dismiss the idea of the Legislature becoming more involved beyond the money lawmakers have already dedicated to the system and other changes they’ve passed, such as adding two seats to the MBTA board.

“We’ve done the things around the edges. Now maybe it is time to sit down and have a hard, frank discussion with the folks that are running it as to how we proceed,” he said. “As of now, every day it’s something different.”