LEWISTON – Lewiston-Auburn could settle on one plan for a new Maine Turnpike interchange by the fall, transportation officials say.

City and state officials and local volunteers are scheduled to begin narrowing a list of six possible downtown interchange designs at a public advisory committee meeting on March 7. Don Craig, director of the Androscoggin Transportation Resource Center, said the group will work over the summer weighing each of the alternatives.

“In the end, our goal is to find the single most practical alternative,” he said. “We hope we’ll get there.”

But Bob Thompson, executive director of the Androscoggin Valley Council of Governments, said there is still a lot of work ahead.

“Planning this kind of transportation project takes years and years and years and years,” Thompson said.

The effort has been under way for more than five years already. AVCOG and the Androscoggin Transportation Resource Center have looked at computerized travel-volume estimates, land-use and development trends, and available land for construction hoping to come up with the right place and design.

Their six plans combine three basic ideas: Building a full interchange on one side of the river; building a river-spanning interchange complex and building a new bridge over the river somewhere between South Bridge and an interchange.