The study, expected to take about eight months after a consulting firm is chosen, will cost as much as $2 million and will provide updated cost estimates and outline the benefits to riders.

The start of the bidding process marked an incremental but important step for the project, known as the North-South rail link. The state’s transportation secretary, Stephanie Pollack, said the study “will help determine if further technical and financial analysis for the project is warranted.”

State transportation officials began soliciting bids Wednesday to study a proposed rail tunnel connecting North and South stations, a long-discussed project that would create an unbroken rail route from Maine to Washington, D.C.


Discussions about the nearly 3-mile tunnel go back decades, but the cost has been seen as prohibitive. Previous estimates placed the cost of the project at $8 billion, but supporters say that advances in construction technology would lower the cost to between $2 billion and $3 billion.

In 2003, governor Mitt Romney shelved the project as too expensive, and its fate seemed sealed. But aggressive lobbying from supporters, including US Representative Seth Moulton and former governors Michael Dukakis and Bill Weld, has brought the proposal back into the public conversation.

Critics call the project a pipe dream, and its future seems doubtful. Governor Charlie Baker has made it clear that he isn’t a big fan and favors a proposed $1.6 billion expansion of South Station that would add seven tracks to the congested hub.

The MBTA faces chronic budget woes and is already seeking to build a $2.3 billion Green Line extension into Somerville and Medford, a project that has been delayed over rising cost estimates.

Pollack said that even as the state is moving ahead with the study, “The MBTA remains strongly committed to making the investments necessary to maintain and upgrade its existing rail and bus services.”


Paul Regan, executive director of the MBTA Advisory Board, which represents the communities that receive MBTA service, said the state should “absolutely not push for the North-South rail link.” He expressed doubts that Boston would be eager to disrupt the city’s transportation system for an underground tunnel, as it did for the Big Dig.

“I don’t think there’s a critical need for it, especially when you compare it to other critical needs,” he said. “The MBTA would go broke; the benefits are really very sketchy. Why are we having this conversation again?”

But supporters say connecting the city’s two rail hubs would greatly improve efficiency.

Moulton spoke in favor of the project last fall, calling it “the most significant infrastructure project contemplated for the New England region.”

“North South Rail Link has the potential to fuel the growth of our economy and connect people with both jobs and housing across the state,” Moulton said Wednesday. The state needs to invest in transportation infrastructure to remain globally competitive, he added.

Proponents say the connection would increase MBTA ridership by nearly 100,000, easing congestion on the roads.

State Senator Jamie Eldridge, an Acton Democrat, said he appreciated the renewed interest in the project but would continue pushing for the state to conduct an environmental review. That would allow the state to secure the right-of-way necessary for the project, he said.

“I think that this does signal greater interest by the administration, but I also recognize that there needs to be more conversations and more advocacy,” he said.


Advocates for more transportation funding said they welcomed the study.

Rafael Mares, a vice president at the Conservation Law Foundation, an environmental advocacy group, said a new cost estimate will make the debate more specific.

“You have to understand that it doesn’t make a lot of sense for the commuter rail lines in the north and the south to not be connected,” he said.

More broadly, the area’s transportation system deserves a more comprehensive approach, he said.

“There’s a lack of vision for our region right now,” he said. “We’re doing our decision-making on a case-by-case basis, and we’re not trying to look at the bigger picture.”

Jon Chesto of the Globe staff contributed to this report. Nicole Dungca can be reached at nicole.dungca@globe.com. Follow her on Twitter @ndungca.