GOV. CHARLIE BAKER followed through on a first-term campaign promise on Monday by dedicating more than $1 billion in state bond funds to the South Coast Rail project, which is now expected to be completed after his second term ends.

The funding commitment followed three cost and schedule reviews of the commuter rail project and the development of a consensus cost estimate of $1.047 billion, up from an earlier estimate of $935 million. The review also concluded that it would take a year longer to complete rail service between Boston and Fall River and New Bedford, moving the completion date from late 2022 to late 2023.

Transportation Secretary Stephanie Pollack said the US Army Corps of Engineers has approved the final federal permit needed for the project to proceed. With the permit in hand and a financing plan in place, Pollack said, the project will be able to move forward quickly. “It’s full speed ahead on South Coast Rail,” she said.

Joseph Sullivan, the mayor of Braintree and a member of the Department of Transportation board, heralded the announcement after 25 years of waffling back and forth on the project by state officials. “For once we can finally say South Coast Rail is going to be built,” he said.

The financing plan represents a huge commitment by the governor. He was already planning to boost transportation capital spending over the next five years, including funding increases for next year of $300 million for the Department of Transportation and $373 million for the MBTA. But now he intends to toss another $1 billion into the mix without requiring his transit agencies to trim back elsewhere.

“It is not a zero-sum game,” Pollack declared, adding that the governor’s decision shows how spending on transportation can go up without raising additional revenues, presumably a reference to the tax and fee increases that are the talk of Beacon Hill.

But Pollack did acknowledge that the governor’s decision on South Coast Rail represents a choice of priorities. Baker’s plan will be funded with nearly $461 million in state general obligation bonds and another $549 million in rail enhancement bonds, which are financed by gas tax money.

The general obligation bond money will come from expected increases in the so-called bond cap (basically the amount the state can borrow) over the next five years. One analyst said the governor’s approach means all of that new borrowed money will be going to South Coast Rail and none to other projects in state government.

“It is a choice,” Pollack said. “The governor made South Coast Rail the top priority for the use of available new bond cap because he feels it was a promise made to that region a very long time ago and it’s time for someone to keep the promise.”

But there are many who wonder whether the governor’s campaign promise is the wisest use of the funds. Others worry the line will fail to attract enough customers, generating annual deficits that will require enormous ongoing subsidies. Pollack said state officials never gave any consideration to asking New Bedford and Fall River to chip in money for the project in the way Somerville and Cambridge supported the Green Line extension.

The South Coast Rail project would extend the Middleborough/Lakeville commuter rail link to Pilgrim Junction in Middleborough and then over to East Taunton before heading south to Fall River and New Bedford over reconstructed rail lines. The project calls for the construction of six new stations and two new layover facilities for the diesel-powered trains that will provide service on the line.

The Middleborough-focused South Coast Rail service is officially described as Phase 1, with Phase 2 to be an all-electric service extending the Stoughton Line with an estimated total project cost of $3.2 billion. Pollack gave no update on Phase 2 during her presentation Monday; Phase 2 had been scheduled to be completed by 2030.

Once completed, the trip between New Bedford and South Station on the South Coast line is expected to take at least 90 minutes. There will only be three peak AM and PM trips each day, with a total of 13 total trips. Ridership projections have been iffy, with estimates of 1,600 daily riders in 2030 and 3,900 in 2040.

Joseph Aiello, the chairman of the MBTA’s Fiscal and Management Control Board, asked James Eng, the MassDOT employee who has been overseeing South Coast Rail so far, what it would cost to operate and maintain the South Coast Rail line once it is completed. Eng said he didn’t have that information, and probably wouldn’t have it for at least three months.

“That’s totally unacceptable,” said Aiello, who has been wary of committing to big projects without first having an idea of the long-term operating costs.

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