WESTPORT — A long-term plan released in July by the Federal Rail Association laying out the route of new high-speed train infrastructure, known as the New Rochelle to Green’s Farm bypass, including a “modified” hub somewhere in the vicinity of the latter station, has raised the concerns of town officials and residents.

“I understand New Rochelle. Why Green’s Farm? Why did they decide on Green’s Farm, of all the places in Fairfield County? Why not Bridgeport, or the middle of Connecticut, or something?” Jennifer Rubel, of Westport, asked at Town Hall at a Monday night information session on the proposed project, hosted in conjunction with the town of Westport, the Westport Historical Society and the Connecticut Trust for Historic Preservation.

The reason, according to Gregory Stroud, head of the nonprofit preservationist group SEacoast, likely has to do with a 29-mile right-of-way owned by the state in the area.

“They have to join the corridor someplace. I think it’s a great question for the FRA,” Stroud said, prefacing his response by saying he does not like to guess at the FRA’s plans.

A problem with the “modified” Green’s Farm station — which is mentioned in the FRA’s Northeast Corridor Reason of Decision, approved July 12 — is that the language of the document is vague and the details of the project are unclear.

“There will no doubt be economic benefits to Connecticut as a whole, and Fairfield County, by having a transportation system that is considered to be faster and more effective,” First Selectman James Marpe said. “But at what cost?”

The entire NEC plan, which could connect Washington, D.C., to Boston, would cost in excess of $150 billion, according to Stroud, and would likely not be completed in the next decade, if not longer.

The project is in Tier 1, meaning the outline, as described in the Reason of Decision, has been released. Tier 2 will occur when the project is broken down and completed in small segments, including the securing of funding, completion of environmental impact studies and contracting of projects by the state with aid from the federal government, so long as the work conforms with the FRA’s plan.

According to Stroud’s research of the plan, in addition to changes at the Green’s Farm station, Fairfield County could see many aerial structures built along, and above, Interstate 95 as a way of easing congestion on the existing Metro-North tracks. Stroud guessed Amtrak trains that run along Metro-North lines would operate on the proposed aerial tracks, making more room for commuter trains that are estimated to reach capacity in Fairfield County by 2030.

Stroud and Marpe both acknowledged a need for improvements, but with few firm details, other than the route, available, voiced uncertainty as to whether this was the proper improvement to make.

Working with towns in Southeastern Connecticut and Rhode Island, Stroud was able to force the FRA to abandon plans along that region of the NEC that would have built over significant historic districts.

In Fairfield County, Stroud is working with heads of towns and cities and residents to create a response and to possibly appeal the FRA’s decision — which could give municipalities more power in developing a plan and studying impacts — before 150 days have elapsed, leaving Westport with an early-December deadline.

Stroud, who called himself “firmly pro-transit,” said the state has final say as to whether or not the projects are built. But, because of the state’s financial woes, and the incentive provided by the FRA to contribute $80 out of every $100 to projects conforming to the FRA plan, alternative plans are unlikely.