Updated 7:25 p.m. Aug. 3

The MBTA will shut down the Orange Line for 30 days, an unprecedented move for one of the T's busiest lines. The shutdown will begin on Aug. 19 at 9 p.m. and is scheduled to end 30 days later in time for the morning commute on Sept. 19.

At a briefing at the Wellington Yard maintenance facility in Medford today, Gov. Charlie Baker and MBTA General Manager Stephen Poftak said the monthlong closure would permit work to be completed that would otherwise take five years if done only during overnights and weekends.

The accelerated work will involve replacing long sections of track, switches, signals and power systems. Once completed, officials promised riders can expect much faster and more reliable service. Poor track conditions have forced speed restrictions and consequently lengthened travel times.

Riding the Orange Line shortly after the announcement, Danielle Membrino of Melrose said she supported the decision.

"I mean, I think the Orange Line definitely needs some work after that fire and all the bad things that have been happening with it. But hopefully, they'll get the work done that they need to," she said. "I'm glad I don't have to commute for work, but I feel really bad for people that do."

Vivian Dang, who lives in Malden and commutes daily to work in Boston, said she wants the transit agency to be more transparent. She heard about prior plans to temporarily shut down Orange Line service, then didn't hear when plans changed, and now she doesn't understand what exactly the work entails.

“I just feel really clueless right now," said Dang, a Malden resident who commutes daily to work in Boston. "They say that the shutdown is to repair the trains and to allow better safety measures, but I don’t really know what that entails."

Poftak said that most of the cars to be deployed on the rebuilt Orange Line will be replacing some of the T’s oldest, many of which are more than 40 years old. The Orange Line has had frequently malfunctions over the summer, with one train catching fire in July when a piece of metal fell from an old car and connected with the third rail.

Officials admitted the shutdown of service will be disruptive for the more than 100,000 daily riders. As an alternative, they are encouraging riders to consider the commuter rail, which runs parallel to the Orange Line along some stretches. The number of trains will be increased on the Haverhill and Providence Lines, and riders will be able to use Charlie Cards when traveling in Zones 1, 1a and 2, which will be less expensive than the usual commuter rail fare.

Buses will also play a crucial role in providing an alternative for riders, though officials were vague about plans, saying more information will be available soon. Details are still being worked out in Boston and other affected municipalities to ensure buses can move as freely as possible, which may mean creating more designated bus lanes. The MBTA signed a $37 million contract with A Yankee Lines Inc. to provide up to 200 buses that will be available to riders at no cost during the shutdown.

The Federal Transit Administration, which is currently conducting an investigation into the T's safety practices, has been notified of the work. An accelerated pace of repairs is something the federal agency had previously recommended.

This story was updated to include comment from Orange Line riders.