The T is getting slower. 83 speed restrictions cover 10 miles of track.

The MBTA added 39 new speed restrictions in February, making the region’s already-slow subway system even slower.

The T’s latest slow zone report shows 26 restrictions were lifted in February, bringing the total open restrictions to 83, an 18.5% increase over the 70 that were active at the end of January.

Slow zones covered 10.1 miles of track as of Feb. 28, bringing the total amount of speed-restricted subway track to 7.5%. By comparison, 8.7 miles, or 6.5%, of track was slow in January, the report stated.

“The slow zone restrictions are in place for the safety of MBTA customers,” T spokesman Joe Pesaturo said. “After repair work over the past couple of weeks, the MBTA was able to lift several speed restrictions that were implemented after the ultrasonic inspections.

“More work is set to take place in the coming overnight periods.”

The once slow-zone free Blue Line now has two, but speeds continue to be slowest on the Red Line, which had 37 restrictions in place as of Feb. 28 — 10 more than what was in place during the first month of the year.

Pesaturo said ultrasonic rail flaw detection equipment, which is sometimes used during regular MBTA track inspections to expose damage that’s invisible to the naked eye, led to 25 additional speed restrictions last month.

Many of these impacted the Red and Blue Lines, the only subway lines with a net-slow-zone-increase in February.

“MBTA ultrasonic technology found signs of wear, including cracks not seen visually, which warrant speed restrictions until repairs can be made,” Pesaturo said. “These cracks are not hazardous for train travel at the current time, as speeds in these areas are reduced.”

Fifteen of those 25 restrictions have been lifted, and the 10 remaining slow zones — nine on the Red Line and one on the Blue Line — will be lifted over the next two weeks, if the weather is favorable for scheduled work, the T said.

Five miles of Red Line track was speed-restricted as of Feb. 28, compared to 3.8 miles in January. Three speed restrictions are also in place on the Mattapan Line, a trolley system that is part of the Red Line.

Trains are traveling 10 to 25 mph in those speed-restricted areas on the Red and Mattapan Lines. A 10 mph and 25 mph restriction are in place on the Blue Line, covering 1,046 feet of track, the report stated.

Trains are still traveling the slowest on parts of the Green Line, which has 18 total restrictions, limiting speeds to 3, 5, 6 and 10 mph over 1.5 miles of track.

The Orange Line, which was shut down for 30 days last summer for track repairs, is the most speed-restricted percentage-wise.

Twenty-three slow zones cover 12.8% of the track, narrowly beating out the 11.9% of speed-restricted track on the Red Line, the report stated.

Stacy Thompson, LivableStreets executive director, said she expects slow zones to persist for a “couple of years” across many different lines.

“These issues did not happen overnight,” Thompson said. “This backlog has been piling up for years, and there is just no way to do this immediately.”

She expects most upcoming track shutdowns will take place on the Red Line, which is most in need of repairs. The Orange Line was targeted last year for this same reason, she said, but a similar 30-day shutdown is not likely.

Thompson said riders have told her they appreciate the MBTA’s new transparency around sharing slow zone data, a shift that started last month. But persistent slow zones are deterring some people from taking the T as often as they used to.

The public would like to know more about the agency’s plan for future diversions, and how long current speed restrictions will remain in place, she said.

“I’m not surprised by the additional slow zones,” Thompson said. “I think that all we’re really seeing is that, for the first time, the T is being transparent about the slow zones on their various lines.

“And we have something in writing that affirms what riders have been experiencing for well over a year now.”