PORTLAND, Maine — A long envisioned passenger rail service connecting Portland with Auburn took another important step forward Thursday as a national Realtors group announced it has awarded a grant to study, in part, new ways to fund the 29-mile public transit line.

The promise of a Portland-to-Auburn line has been quietly evaluated in recent years, but has been largely overshadowed in the media by the extension of Amtrak’s popular Boston-bound Downeaster train from Portland up the coast to Brunswick.

Tony Donovan, founder and president of the Maine Rail Transit Coalition, said the newly announced $15,000 National Association of Realtors grant will build off of a federally funded study of public transportation options north of Portland completed in 2011. It also will be used as seed money to leverage an additional $60,000 to $70,000 to explore the proposed rail line, he said.

Donovan described the $15,000 grant, despite being small in size, as a “game changer,” as it provides the push necessary for the Portland-to-Auburn rail plan to build momentum. Previously, he said, it remained a long analyzed, but otherwise stagnant, proposal.

Among the focuses of the newly funded research work will be a look into utilizing so-called “value capture” methods of funding the transit expansion in Maine. The model involves recouping investment into the rail infrastructure by capturing additional tax revenues generated by raising property values along the rail corridor.

The plan essentially would be a transportation-focused tax increment financing program. Municipalities and private developers commonly use TIFs to shelter property tax increases — spurred by new development — from being collected by the state government, instead protecting the extra taxes for local reinvestment of some kind.

Donovan — who is also a board member of the Maine Commercial Association of Realtors, the local administrator of the national association grant — said property values increase along rail corridors as residents have easy access to transportation and businesses get easier access to potential train-riding customers.

Another potential strategy included in the value capture model involves approaching businesses benefitting from the customers or employees being delivered by the rail to help cover the costs of the service, Donovan said.

The state of Maine owns the railroad currently in place connecting Portland with Auburn.

“We’re saying maybe there’s a way to generate funds for transportation at the local level, and not only could we change the way we fund transportation, but change the way we make decisions about transportation,” Donovan told the Bangor Daily News. “We believe that if an alternative [to highway travel] is available, there are a lot of people who will want to use it and who will pay to use it, and who will find that their cost of transportation is less than that of owning a car.”

Portland City Councilor David Marshall serves on the Greater Portland Transit District board and is chairman of the city’s Transportation, Sustainability and Energy Committee.

“I think it’s important for us to look at transportation choices for people, and this particular rail line serves as a connection between the two largest metropolitan areas in the state, being Portland and Lewiston-Auburn,” Marshall said. “Our roads get a heavy amount of use. Every passenger car and truck we can take off the roads means less pressure on them, and they’ll last longer as a result. But there also are increasing numbers of families living without cars, so the timing is good to look at other commuter options throughout the region and see what the viability is.”

Donovan said the initial study will consider potential funding for, as well as the economic and environmental impacts of, a commuter rail service featuring 22 round trips daily between the two cities using smaller diesel rail cars with capacities of approximately 100 passengers each. The Diesel Multiple Units, or DMUs, would travel between 60 and 80 miles per hour through the corridor, Donovan said, although they could have a much higher maximum speed.

Long-term, he said, connecting Portland with Auburn would set the stage for future northwestern expansion to the fledgling Oxford Casino, ski resorts like Mt. Abram and Sunday River, and even perhaps all the way to Montreal, Canada.

The Maine Rail Transit Coalition president acknowledged that project skeptics may be quick to point out the estimated $60 million-$70 million cost of establishing the Portland-Auburn line — a sum that would cover, among other things, the reconstruction of the railroad, acquisition of the DMUs and building of the platforms along the way.

But he said Maine is well-positioned to access as much as $75 million in U.S. Transit Authority funding for the project from the same New Starts/Small Starts grant program that funded the aforementioned study into public transportation options north of Portland.

A federal program like that, Donovan said, could require a 50 percent match from the state or local governments. But he said when the costs of the proposed Auburn-to-Portland line is compared to the costs associated with maintaining roads and bridges, Mainers might be convinced to support the investment.

“Relatively speaking, the cost that we’re talking about investing in this type of transportation is less than what we’re talking about spending on roads and bridges, and we believe the numbers indicate a better return on investment than spending on roads and bridges,” Donovan said. “Even 50-50 is a manageable bond. People say, ‘Oh, $60 million,’ but you’re paying more than $20 million to replace the Martin’s Point Bridge [between Portland and Falmouth] and that’s only a third of a mile.

“We believe this will be the basis for a transportation system that will attract jobs, attract new wealth and new economic development,” he continued.