The assumption among many Mainers has been that rail travel could never usurp car travel, or even augment it to any real degree, because of the state’s relatively small population, low building density and perhaps the lack of parking and traffic issues that drive people to public transit.

The Maine Rail Transit Coalition thinks otherwise. The group will have a chance to make its case in the coming months, as the debate begins about the future of a 30-mile rail line from Portland to Auburn where freight service soon will be discontinued.

The coalition’s plan for commuter rail service along the corridor would require significant public investment and help from private investors. But rail service between Maine’s two largest population centers could increase property values and spur business development. It could take cars off the road, lessening their environmental impact and lowering the cost of maintaining roads. And it could provide a starting point for a larger-scale public transit system that benefits much of the state.

But first, a lot of questions must be answered. The obvious question is whether a rail system can work, given the demographic realities in Maine. The coalition says it can, and has elsewhere in areas much like Maine, which itself has seen ridership for the Portland-Brunswick Downeaster train exceed expectations in its first year.

The population of the Portland-to-Auburn corridor is around 250,000. The coalition points out that the rail corridor from Beaverton to Wilsonville, Ore., has a population of 440,000. The commuter rail in Santa Fe, N.M., has 396,000 people.

Both these commuter lines have found fans and experienced ridership growth, but they also have been criticized. Some of that has been based on mismanagement and a failure to meet stated goals. Most of the criticism, however, is centered on cost. Part of that is cultural, as taxpayers see money spent on rail service as a subsidy, while they have no problem spending billions of dollars on road upkeep.

Tony Donovan, a founder of the Maine Rail Transit Coalition, points out that maintaining roads costs around $1 million per lane per mile, and work must be completed every 10 to 12 years. Railroads also cost about $1 million per mile to maintain, but only every 40 to 50 years. That could save a lot of money, and a lot of wear and tear on the heavily traveled roads between Portland and the Lewiston-Auburn area, as long as people can be convinced to ride the rails.

To entice riders, the service would start on India Street, near downtown Portland, and at the Port of Portland, where cruise ships dock, and include stops in Falmouth, Yarmouth, Pineland in New Gloucester, and at the Auburn airport. Donovan said additional amenities, including transportation features such as buses, rental bikes and pedestrian opportunities, would build up at the stops, with the communities’ input. The line eventually could extend to Montreal.

The coalition is lining up private investors for the train platforms, stations and equipment, for a total of $20 million. A $27 million state bond would leverage the federal funds needed for the rest of the estimated $138 million project. Operations could be paid for in part by assessments on property value increases that occur because of the nearby rail service. The Department of Transportation is working on a report detailing funding mechanisms for design and engineering work.

If it comes to it, the transportation bond would have to be approved at the statewide ballot. The bond should stand on its own, so Maine can give the project a clear up-or-down vote.

Until then, Mainers should press for more information about how the rail service would enhance the communities along its path, and how the supposed benefits to energy efficiency and transportation costs would be measured and held in account.