Building a 5-mile toll highway linking the Maine Turnpike to the suburbs west of Portland could cost almost 60 percent more than expected but will still generate enough revenue to pay for itself, a turnpike official says.

The Maine Turnpike Authority board of directors last week authorized staff to negotiate land purchases for the Gorham Connector, a limited-access highway designed to alleviate commuter traffic on local roads.

The proposed road would connect the turnpike exit near the Maine Mall in South Portland to Route 114, south of Gorham.

By its projected opening in 2026, the four-lane highway will cost at least $191 million and as much as $237 million, according to a report this month from HNTB, an infrastructure design firm. That exceeds the $150 million that the Legislature approved two years ago for construction borrowing for the project.

Despite higher prices than projected, a new $1.50 toll route would pay for itself and bring tens of thousands of vehicles off surface roads and onto the state’s main highway, said Peter Mills, executive director of the turnpike authority.

“Even at a higher construction cost, it still works,” he said. “Why? The traffic is crazy out there.”

Morning and afternoon rush-hour congestion is a major headache on Routes 25, 22 and 112, local two-lane roads connecting Portland and growing towns such as Gorham, Buxton and Standish.

A 15-mile trip from downtown Portland to Buxton that takes a little less than half an hour at midday can turn into an hourlong, bumper-to-bumper slog around 5 p.m., according to a Google travel projection.

In the last three decades traffic on Routes 25 and 22/114 east of Gorham have grown almost 30 percent, according to Maine Department of Transportation. Almost 9,500 more vehicles use those roads daily than in 1990. Two years ago, HNTB reported traffic was projected to grow by another 20 percent in the region by 2040.

“At Maine DOT we are concerned about the volume of traffic on the roads west of Portland,” said spokesman Paul Merrill in a statement.

“That traffic represents one of the worst commuter congestion problems in Maine. The Gorham Connector project is still in its early stages, but we see it as a promising opportunity to try and relieve some of that congestion.”

The turnpike is considering a new road at the same time Maine is pursuing goals to significantly reduce fossil fuel emissions. Academic research has shown new road construction creates more traffic because it encourages people to drive.

In the long term, the solution is land use policies to encourage dense, multi-use development focused on public transit and pedestrian access to jobs, education and shopping, Mills said.

“The problem is, the sprawl is already there. The question is what are you going to do about it – now we are in a reaction posture,” he said. “Future policy is not going to relieve the need for this highway.”

Expanding local roads was explored by the state about seven years ago, but a new turnpike spur was chosen because of the cost, environmental damage, disruption to community centers and dislocation of property owners from expanding lanes.

Lawmakers in 2017 gave the Maine Turnpike Authority permission to start planning the new spur and borrow money for the project.

When it opens in 2026, the Gorham Connector could add almost 35,000 vehicles daily onto the turnpike, according to the most recent HNTB report. In rough terms, the turnpike would be earning $13 million annually in toll revenue from the spur and turnpike traffic increase, Mills said, enough to pay off bonds sold for the project.

The higher costs of the project were expected, Mills added. Construction costs in southern Maine have surged in recent years, driven by scarce skilled labor. This past summer, Maine DOT canceled road and bridge work worth tens of millions of dollars because contractors’ prices were too high.

“When we were given permission to build this they increased bonding capacity by $150 million,” Mills said. “It doesn’t look like it can be built for $150 million; it is north of $200 million. Even at this stage we are projecting what it would cost to start construction three to four years from now.”

The turnpike won’t start construction on the spur until it completes widening about 5 miles of the turnpike around Portland from four lanes to six, in an effort to combat congestion there.

Officials are already in talks with property owners to purchase parcels near the end points of the proposed Gorham Connector, Mills said. A precise road route will depend on land purchases, landscape and environmental constraints.

The project has been a long time coming, but there are legitimate concerns it will only encourage more traffic, said Gorham Town Manager Ephrem Paraschak.

“The reality is our road infrastructure at the local and state level is at a breaking point,” Paraschak said. Gorham has been working on its land-use policies to discourage sprawl and the town got its first regional public transit connection last year.

But right now, people depend on overwhelmed local roads to get around, Paraschak said.

“The reality is, people have to get into Portland,” he said. “Even when the Gorham Connector happens, we hope it will be a quicker route for shuttle buses and public transit as well.”