THE MBTA is considering a proposal to slightly widen the tracks on most of the Green Line extension to Somerville and Medford by shutting the system down early for 10 to 14 days starting November 1.

General Manager Phillip Eng  told the MBTA board of directors on Tuesday that the T’s contractor has proposed shutting down the system at 9 p.m. and “re-gauging” the tracks until 5 a.m. Eng said the T is studying the proposal and has not made a final decision yet on whether to proceed.

The work would involve pulling up the rails, adjusting the metal clamps on the rail ties to the proper width, and replacing the rails.

Eng stressed that trains on the Green Line extension can operate safely at top speed now even though the distance between the rails on much of the line is less than what the contract specifies. He said the goal is to get the track widths back to construction specifications to avoid problems down the road, suggesting the rails narrow over time.

The T says its contractor flagged the narrow width of sections of the track in April 2021 and again in November 2022, before the Green Line extension was fully opened. Eng has been critical of T officials for fixing problems identified at the time but failing to address the broader problem.

Eng has blamed the narrow gauge of the rail on the way it was fabricated at the factory.