Scrapping plans to overhaul railcars that date back to the 1990s, the MBTA agreed on Monday to replace its entire Red Line fleet by 2024 by purchasing an additional 120 to 134 cars at a cost of up to $280 million.

T officials presented the proposal to the MBTA Fiscal and Management Control Board, saying it would be less expensive per-car and more beneficial than their prior plan of making overhaul repairs to 84 Red Line cars.

The board approved the proposal unanimously on a voice vote.

Transportation Secretary Stephanie Pollack told reporters the plan represents a new way of doing business at the T. “It represents what we’ve been trying to do with the MBTA. A different way of thinking, a different way of acting,” Pollack said, adding that the decision was the result of “working backwards from strategic targets” of shorter times between train arrivals.

The move would increase the MBTA’s current order from Chinese railcar manufacturer CRRC, which is under a roughly $565 million contract to build 132 Red Line and 152 Orange Line cars at a facility in Springfield.

When all the new vehicles are on the system, the MBTA will be able to run trains faster, significantly increasing capacity on the line running from Braintree and Ashmont to Cambridge during rush hour, MBTA Chief Operating Officer Jeff Gonneville said.

Red Line commuters frequently face jam-packed trains and service delays on their way to and from work.

The possibilities of a new fleet by 2024 were discussed during an MBTA Board meeting and briefing in September. At the time, officials said the MBTA’s busiest subway line could transport an additional 10,000 passengers an hour and keep the time between trains to about three minutes if the agency upgraded the line’s entire fleet. The 50 percent boost in capacity would mean less congestion, especially in the system’s downtown Boston core, for the 150,000 riders who rely on the line each day, with demand on the rise as housing is built near Red Line stations in Quincy, Dorchester, and Cambridge.

With an entirely new fleet by around 2024, the T would be able to consider futuristic upgrades along the Red Line, such as doors built into the station platforms or autonomous vehicles, Gonneville told reporters. He said parts on the new Red Line cars would be interchangeable with the new Orange Line fleet.

“It sets the foundation for future opportunities,” Gonneville said. The Orange Line fleet will be completely replaced and increase in number under the existing agreement with CRRC.

The proposed new agreement with CRRC is for 120 new Red Line cars, which the company would start building right after completing the original order.

In total the new purchase will cost about $280 million, according to the T. The agency would also have the option of purchasing an additional 14 cars, which would vary in price, according to the T.

Gonneville said the option gives the T “flexibility.” Without taking the options, the Red Line would have a total of 252 new vehicles, including 42 spares, in 2024, he said.

“If someone looked at this they’d say it’s a no-brainer, but in fact there’s a lot of brainers,” Braintree Mayor Joe Sullivan, who is a member of the Massachusetts Department of Transportation board of directors, told the control board. He said, “This is a wise decision financially, operationally.”

Quincy Sen. John Keenan was among those offering his support for the plan at the meeting. “You end up with an entire new fleet,” Keenan told the control board. He said, “That is an enormous and important opportunity.”

State Sen. Linda Dorcena Forry and state Rep. Nick Collins of South Boston joined in the applause. “The investment in new Red Line trains will significantly improve efficiency and reliability for all commuters, in particular my neighbors in Dorchester, South Boston and Mattapan,” said Forry. “I commend the MBTA for taking steps to modernize the system and improve the service for riders.”

Added Collins: “This is an important step forward for the system, and one that will greatly enhance the quality of life for commuters in South Boston and Dorchester. … The Red Line is a key transit corridor that keeps our city and our region thriving, and this sort of investment will ensure that it will be a reliable connection for residents, businesses, and commuters for years to come.”

Pollack said without acting quickly there was a risk CRRC would take a contract from another railcar customer and the T would need to wait for that work to be completed. She said buying directly from CRRC would avoid the cost and time spent on going out to bid and said the board has been briefed in closed-door executive sessions on legal implications of the move.

The T would use $59 million from its pay-go capital fund for the purchase and then do a bond offering of about $220 million, MBTA Acting General Manager Brian Shortsleeve told reporters. Pollack said the capital plan had included about $220 million for overhauling 84 Red Line cars. The purchase plan will require an additional $36 million to keep the older Red Line cars in working order before the new cars are delivered, according to the T.

“We do have the debt capacity,” MBTA Chief Financial Officer Michael Abramo told the control board.
With more than 280,000 trips per weekday the Red Line is the busiest line on the MBTA. The 84 vehicles date to the mid-1990s and are the newest cars on the Red Line, according to MBTA data.

While advocates press the MBTA for expanded service, Gov. Charlie Baker and Pollack have made a priority of improving service on the existing system.