PORTLAND – A multimillion-dollar plan to improve Interstate 295 between Scarborough and Brunswick is drawing criticism from activists opposed to widening some sections of the road from four lanes to six.

Other elements of the I-295 Draft Corridor Study, still in draft form, call for reworking key interchanges and making exit and entrance ramps safer.

The state Department of Transportation began its study of the stretch of highway in 2000 at the direction of the Legislature, which was concerned about higher traffic volumes. Some 75,000 to 85,000 vehicles a day travel the route between South Portland and Portland and 50,000 use the part between Falmouth and Brunswick.

Projections calling for a 20 percent increase in traffic over the next 20 years have spurred concerns that portions of the road may have to be widened.

Community and environmental activists suggest that a greater emphasis on public transportation could obviate the need for additional pavement that would accommodate more cars and generate more pollution.

“This study is coming out with a bias toward single-occupancy vehicles,” said Alec Maybarduk, a field organizer for The League of Young Voters, a Portland-based political action group.

Christian McNeil, vice chairman of Portland’s Bicycle and Pedestrian Advisory Committee, is advancing a radical plan to discontinue I-295 through the center of Portland and convert that stretch to a 25-mph boulevard that is friendly to pedestrians and bicyclists.

“I just don’t think it makes sense to have it go through downtown Portland,” said McNeil, who believes it would be “irresponsible” to spend money that’s needed to repair the state’s existing roads and bridges on a few miles of I-295.

The cost of widening the highway from four lanes to six from Exit 2 in South Portland to Exit 9 in Portland is estimated at $50 million; from Exit 11 in Falmouth to Exit 15 in Yarmouth, it’s pegged at $18 million.

Ed Hanscom, project manager for the study, said the widening plans are long-term and the study does account for such alternatives as commuter rail north of Portland and rapid transit bus service.