Less than one year after the final branch of the much-heralded Green Line extension opened for business, the MBTA said a problem with the tracks has reduced train speeds to just 3 miles per hour along stretches that add up to more than a mile.
Even by the T’s low standards in recent years, it’s an extraordinary development: Tracks that opened for passenger service to Union Square in March 2022 and to Medford last December and were shut down for repairs in recent months are now so defective, the T says, that trains are moving more slowly than many people walk.
T spokesperson Joe Pesaturo said the new slow zones, 11 on the Medford branch and 3 on the Union Square branch, are necessary after inspections this month found the rails are too close together at many spots. Operating trains at full speed on tracks that are too narrow risks derailment, track experts said.
But experts told the Globe that rails typically become wider, not narrower, with wear and tear.
Robert Halstead, a New York-based railroad accident reconstruction expert with Ironwood Technologies, said it’s very unusual for rails to narrow.
“You got me there,’’ said Halstead, who has been inspecting rail tracks for more than 40 years. “That’s something I don’t generally see.’’
It was not immediately clear how long the defects have been in place.
Pesaturo said the gauge, the width between rails, on the Medford branch “has been considered narrow since the opening, but there were no known conditions that warranted a speed restriction’’ in recent months.
A March geometry scan of the Green Line extension tracks, which uses a machine to identify defects that might not be visible, resulted in no speed restrictions being implemented, Pesaturo said. He did not say whether that scan found problems.
But a scan in mid-June found six areas on the Medford branch and two at the “Union crossover’’ where the rails were “out of tolerance,’’ he said.
All of the defects identified during the June scan were addressed during the last weekend closure of the branches in June and during some overnight periods in July, he said.
This month, another geometry scan was performed, and more gauge-related issues were found on both branches, he said.
“The MBTA is working to determine the cause of these instances in which adjustments to the rails are needed to maintain the proper track gauge,’’ he said.
Spokespeople for the Department of Public Utilities, the T’s state safety oversight agency, deferred questions to the MBTA.
Riding on the Medford branch Tuesday, Taylor Rossi watched the landscape creep by outside her train from Medford/Tufts Station to Gillman Square in Somerville.
A GLX rider for more than a year, Rossi has come to accept occasional slow speeds, but Tuesday’s crawl was the worst she had ever seen.
“I feel like I probably could have walked faster,’’ Rossi said.
Outside the train, cyclists whizzed by on the community path, and pedestrians kept pace with the trolley.
Rossi said she expected the GLX, “being a newer line,’’ would have lasted far longer before needing maintenance. She said she had no idea what was causing the slowdowns, but she hoped they began “for a good reason: safety, things like that.’’
Shutdowns for track repairs are supposed to yield faster and more reliable subway service. But on the Green Line extension, where riders endured four straight weekends in June without train service, a roundtrip from Lechmere on the new Medford/Tufts branch takes around 10 minutes longer than it did a month ago, according to the TransitMatters dashboard.
The Union Square branch is shut through Oct. 12 to accommodate repairs to a bridge on the McGrath Highway that crosses over the tracks.
The T plans to have the three speed restrictions on the Union Square branch eliminated by the time the branch reopens, Pesaturo said. Repair work to eliminate the 11 speed restrictions on the Medford branch began last week, he said.
“We’re making every effort to resume that work this week,’’ Pesaturo said.
The MBTA has struggled to eliminate slow zones more quickly than it adds new ones. Throughout the entire Green Line, the T added 18 speed restrictions in the last month and eliminated just one, according to its dashboard.
Dysfunction in the T’s Maintenance of Way department, which oversees track safety, is complicating efforts, a report released by the agency earlier this month found.
Maintenance of Way workers responsible for checking subway infrastructure for defects either didn’t understand their responsibilities or didn’t fulfill them and, as a result, missed dangerous problems on vast swaths of the subway as recently as March, the report by an outside expert hired by the T showed. Many workers in charge of inspecting the system’s tracks don’t have enough experience or training, the expert said.
The expert also found that the Maintenance of Way department did not verify or correctly respond to the results of geometry scans done in the second half of 2022 by the time the next round of testing was conducted, in the first quarter of 2023. Defects found by those scans are supposed to be verified by the Maintenance of Way department to eliminate false positives — called “ghosts’’ — and then either repaired immediately or covered by a slow zone until the repair can be made.
Pesaturo did not respond to a question about whether the new Green Line extension defects are the result of those lapses.
Also complicating matters for the T are new limits from federal regulators about when and how the agency can make track repairs after subway trains came dangerously close to workers on several occasions since early August.
The T is no longer allowed to send out lone workers to inspect tracks or make repairs while trains are running except in cases of emergencies, the Federal Transit Administration said in a letter on Friday when it admonished the T for allowing solo workers on the tracks despite being prohibited from that practice by the FTA on Sept. 14.
The T halted some track work last week because of the new restrictions. Pesaturo did not say whether that work has resumed.
Correspondent Daniel Kool contributed to this report.