The MBTA lifted speed restrictions along nine Red Line stretches between its Park Street and JFK UMass stations following service disruptions that enabled crews to expedite track work over the past week.

The T announced Tuesday morning that nearly ten miles of the Red Line remains under speed restrictions, which the transit authority called "a first since March 8 when the MBTA first initiated slow zones systemwide."

The slow zones -- which in this case limited train speeds to 10 mph or 25 mph - are in place because the T determined it would be unsafe to run trains at normal speeds until fixes are made. The latest work involved replacing more than 2,000 feet of rail and 115 rail ties.

Once considered rare, the MBTA is now routinely taking portions of its core subway service offline to make repairs in less time than it would take to make them during overnight shifts. The T believes it can use this approach to address all slow zones by the end of 2024.

Red Line passengers were diverted to shuttle buses while the work was conducted during evenings between Nov. 14 and Nov. 16 and all day over the weekend of Nov. 18-19.

The T also used the work period to paint, clean signs, sand and restore platform benches, install new rubber flooring on the stairway at Broadway Station, and fix "tripping hazards" on the platform at South Station.