During the 30-day Orange Line shutdown, the MBTA replaced 14,000 feet of rail, laid 48,000 feet of new signal cable, readied 72 new Orange Line cars for service — and prompted an untold number of “I’m running late” texts.

The headache for those traveling above ground on shuttle buses allowed crews working underground to get caught up on much-needed replacement of decades-old infrastructure.

If the monthlong closure, which is set to end Monday morning, was a commuting nadir for the people who take around 100,000 trips on the line each weekday, officials say it was worth the sacrifice. They say that passengers on the Orange Line, which runs from Malden to Jamaica Plain, will experience a safer, faster, cleaner, more reliable subway experience when the second-most popular line again welcomes the public.

”To the extent that there are folks who have lost confidence in the T, I’m hopeful that this is a step in regaining that confidence,” MBTA General Manager Steve Poftak told reporters Sunday.

But the track work on the Orange Line is among a list of dozens of fixes the T will have to make in the coming months under directives from the Federal Transit Administration, which began investigating the MBTA this summer after a series of grave safety violations, including the dragging death of a Red Line passenger in April.

A modern system will require more investment in the T’s day-to-day operations, the FTA found, and as many as 2,000 new employees, a massive task for an agency facing a budget gap of more than $200 million starting next summer.

Poftak said the agency is planning diversions of parts of the Green Line and Red Line this fall so the T can operate more smoothly in the future. The Green Line’s Union Square branch, part of the Green Line Extension, will also open back up Monday after four weeks of closure.

Angel Peña, MBTA’s chief of capital transformation, credits the MBTA with doing what had never been done before: shutting down an entire line to get a considerable jump on the enormous maintenance backlog. But, he cautioned, this 30-day shutdown alone will not solve the T’s problems.

“If we are serious about modernizing, that means more sacrifices,” he said during a tour of the track work on Friday. “Do we have the foundation? Yes. Do we need to continue with maintenance? Absolutely.”

Despite waking up earlier and trying to plan ahead, riders said they were still late for work or school while relying on the shuttle buses that replaced Orange Line service. Municipalities along the line worked to create new bus-only lanes, bike lanes, and eliminate parking and car traffic along some stretches to help speed up commutes and encourage alternatives.

Though frustrating, the shuttle bus system seemed to work well enough to avoid any crises. Commuter rail, which the T made free in and around Boston, and the Bluebikes bike share system, for which free passes were offered, saw an uptick in ridership.

The Orange Line work that took place during the 30-day closure was a huge — and the T says hugely successful — effort to fix problems that have plagued the line for years.

Before any work could begin, crews had to shovel, scrape, and carry away three to four inches of grease piled on top of fasteners they aimed to replace, said Desiree Patrice, MBTA deputy chief of capital transformation.

Underneath the grease between Tufts Medical Center and Back Bay stations was a stretch of tracks so defective that it had forced Orange Line train operators to reduce their speed to 10 miles per hour, down from the normal 25, for the last three years, one of six such slow zones along the 11-mile subway line.

This area of the Orange Line caught the attention of federal inspectors this summer who found “evidence of excessive wear and defects” and “corrosion” along the north- and south-bound tracks and ordered the T to make fixes.

Once workers carted off the grease, they power-washed the area, removing any remaining residue, Patrice said. Then they got to work removing clips, jacking the rail up about 24 inches off the ground, and eventually unbolting and replacing around 400 cologne eggs — the egg-shaped fasteners that sit between the rail and the concrete to dull noise and vibration near hospitals — before finally replacing the rail.

On Friday, the shine on the new eggs made them look like an entirely different piece of equipment compared to their rusted predecessors. The old rail lying on the ground waiting to be hauled away had been filed down on the sides after years of friction with train wheels, while the new one was perfectly rounded where it should be, Patrice said. All that was left to do was torque the bolts.

Workers dressed in MBTA-style reflective vests with an X on the back made their way down a narrow staircase into the dark tunnel at the Tufts Medical Center station around 7:30 a.m. Friday. For many, it was their last day in that tunnel during the project before test trains began running over the weekend.

With his left hand on the rail and his right hand around a power tool, one worker bent over and carefully screwed in each of the four bolts on one new egg, then torqued them with a long wrench. Then the crew of three loaded up their cart — a grated platform with wheels that sit on each rail — and dragged it along as they set out to find the next bolts in need of tightening with their flashlights.

Most of the work — pouring new grout, fastening rail to the ground — was done by hand, with an assist from large machines that help haul supplies from only four access points along the line, said Peña. At any given time over the last month, 200 to 300 MBTA employees and contractors have been working along the Orange Line tracks.

Before the work began, Peña said he had 20 meetings and planning sessions about how best to choreograph everything. Since the shutdown began, he’s been on four calls each day: 7 a.m. with contractors, 8 a.m. with upper management, 4 p.m. with contractors, and 5 p.m. with upper management.

On Monday, speed restrictions along the line will remain in place. Poftak said trains should be able to move at full speed within a week of the reopening.

Other changes to MBTA service during the shutdown will remain in place too. Haverhill Line commuter rail trains will continue to stop at Oak Grove station, and more commuter rail trains will stop at Forest Hills station, Poftak said, allowing for two trains per hour to pick up downtown-bound passengers there during the morning rush.

Though Orange Line trains will be able to travel faster, and most of them will be new, they will be making fewer trips than usual. In response to a finding from the Federal Transit Administration in June that its operations control center was dangerously understaffed, the MBTA cut subway service on the Orange, Red, and Blue lines by more than 20 percent. The cuts were meant to be in place for the summer, but the T has been unable to hire enough dispatchers to restore service and has said subway service will be reduced for the fall, too, frustrating riders.

Peña is already eyeing the next set of improvements for the Orange Line, including building more access points for heavy construction equipment so that crews can complete their work faster.

“There’s so much more to do,” he said.

Tonya Alanez of the Globe staff contributed to this report.

Taylor Dolven can be reached at taylor.dolven@globe.com. Follow her on Twitter @taydolven.

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