Electrified trains could roll out on the MBTA’s Fairmount Line as soon as 2028 under a plan agency officials approved on July 25 that represents a delayed but major step toward overhauling the commuter rail system.

The T’s board approved a $54 million agreement with Keolis, the company that operates commuter rail for the organiation, to bring battery electric service to the Fairmount Line that runs from South Station through Dorchester, Mattapan, and Hyde Park.

Officials say the new fleet, once operational, will run service every 20 minutes all day while generating less noise in the neighborhoods through which it passes. The battery electric trains will produce about 17,000 fewer tons of carbon dioxide emissions compared to diesel trains, the T said.

Gov. Healey called the contract “a major win for Fairmount Line riders and our entire state” and MBTA General Manager Phil Eng added, “This agreement is a gamechanger that will benefit generations of passengers, beginning first on the Fairmount Line.

“By embracing new technologies, we will be able to electrify the Fairmount Line sooner within our existing available funding. Understanding the billions of dollars needed to fully electrify our entire system, this is the first step that I believe will pave the way to a profound transformation that can bring the future of our rail network that much closer.”

The battery electric hybrid trains that will eventually run on the Fairmount Line can use both onboard batteries and overhead catenary wires, which also recharge the batteries.

Officials projected the first new trains will begin running on the line in “early 2028,” depending on how procurement goes. About 3,200 passengers rode the Fairmount Line each day in April, according to the T.

Transit advocates celebrated the agreement, describing it as a concrete step toward goals first laid out years ago.

In 2019, the MBTA’s management board at the time voted in favor of electrifying the commuter rail system and running more frequent service in a so-called regional rail model. Their vote called for T officials to prepare immediately to launch electrified pilot programs on the Providence/Stoughton Line, the Fairmount Line and a section of the Newburyport/Rockport Line.

But progress since that vote has been slow, partly because the pandemic upended operations.

“This is a monumental step that represents the first real commitment to the Regional Rail vision laid out five years ago,” said TransitMatters Executive Director Jarred Johnson. “We’re excited that the T is partnering with Keolis to test new technology that allows us to electrify the service faster and bring tangible benefits to riders.”

Commuter rail ridership has recovered more significantly than subways or buses since the pandemic.