The Maine Turnpike Authority has started a process to relieve congestion between Scarborough and Falmouth that could include widening that section of the highway to six lanes.

The action follows a record year for turnpike traffic, which reached an all-time high of 83.6 million vehicles in 2016, a 10 percent increase over two years. Since 2014, traffic in the Portland area has grown 3 to 5 percent annually, increasing “to the point where safety and mobility is becoming compromised,” the authority said.

In some areas, traffic congestion is already causing problems, and officials expect it will get worse in the next decade, Turnpike Executive Director Peter Mills said on Wednesday.

“We have seen really substantial, rapid growth,” he said.

A newly created public advisory committee charged with assisting the authority in assessing the corridor’s needs will hold its first meeting on June 28. It is open to the public.

“The purpose of the first meeting is to bring people up to speed as to where we see the issues and where we see them getting worse in the next year and the year after,” Mills said.

As the process moves ahead, the authority expects to discuss how it intends to fix the issues. That likely will include widening a congestion-prone section between Scarborough and Westbrook, but also will encompass other solutions, like improvements to highway ramps. A final plan will depend on multiple factors, including a proposal to build a spur highway from the Turnpike to Gorham.

“There are some things we can do to address specific congestion points without having to do the widening,” he said.

INCREASING TRAFFIC VOLUMES

A 2016 analysis by HNTB, a Kansas City, Missouri-based engineering company with an office in Westbrook, found that the section of the Turnpike between Exit 44 in Scarborough and Exit 48 in Westbrook will reach capacity within 10 years.

The entire highway from Biddeford to Falmouth will reach capacity within 20 years, the report said. The Portland-area widening “may need to begin in the near future to avoid capacity constraints,” it said.

The turnpike is six lanes between the New Hampshire border and the intersection with Interstate 295 south of Portland, where it becomes four lanes. Last year, Mills suggested the agency would advance its plan to widen the highway because of increasing traffic volumes. A previous plan to expand the Turnpike around Portland was shelved after traffic dropped following the 2008 housing and financial crisis.

COST ESTIMATES

The HNTB analysis estimated that improvements to northbound lanes of the turnpike from the Portland International Jetport to Westbrook could cost $14.6 million and be completed by 2023.

A bigger project to improve southbound sections from Saco to Westbrook, and northbound improvements between Westbrook and Falmouth, as well as improvements to the Saco off-ramp could take until 2032 and cost $102 million, according to the study.

The assessment of the Scarborough to Falmouth corridor comes on the heels of a proposal by Gov. Paul LePage to merge the turnpike authority with the Department of Transportation and move toward a single toll in York. The governor’s plan was rejected by a legislative committee last month.

Last year, Mills said that increasing toll revenue meant the turnpike would be able to fund work in the Portland area without additional borrowing or raising tolls.

The advisory committee is scheduled to meet June 28 from 4-7 p.m. at turnpike headquarters at 2360 Congress St. in Portland.

The committee will take comments and questions from the public.

Peter McGuire can be contacted at 791-6325 or at:

[email protected]

Twitter: PeteL_McGuire