Critics, studies cast doubt on Maine’s claims of climate benefits from highway expansion

Climate and clean transportation advocates are calling into question a claim by Maine officials that a new toll road proposed outside Portland will reduce carbon emissions by alleviating gridlock.

It's a common argument made in favor of highway expansions nationwide, said Benito Pérez, the policy director of the nonprofit Transportation for America. But it relies on a narrow view of data that, in context, tends to show these projects are more likely to increase planet-warming emissions, he said.

"They're looking at it from one dimension," said Pérez, a former transportation planner and engineer. "This is a multi-dimensional issue when it comes to emissions reduction, and it's not going to work."

Maine's proposed Gorham Connector project has met stiff public opposition in its rollout over recent months. The toll road aims to offer a more direct route from Portland's growing suburbs into the city, bypassing local roads that officials say weren't designed to accommodate increasing commuter traffic.

The project has been contemplated since the late 1980s. Its latest iteration builds on a 2012 study that recommended three main ways to improve connectivity between Portland and points west: new approaches to land use and development, expanded bus and passenger rail access, and various road upgrades and expansions, including the new four-lane, roughly five-mile bypass the state is now proposing.

The Maine Turnpike Authority took more than three hours of comments at its first public input session on the project in March. On July 18, the MTA said it would delay further public meetings on the project and extend its permitting timeline due to a "high level of public interest and concern."

In response to questions for this story, MTA spokesperson Erin Courtney emphasized the importance of a multi-pronged approach in achieving the Gorham Connector's projected climate benefits.

"Coupled with targeted land use and transit initiatives, we aim to create a more efficient and sustainable transportation system that addresses both congestion and environmental impacts," she said.

Benefits are 'negligible at best'

The emissions impact of smoother traffic on the proposed toll road has been one of the MTA's core arguments in favor of the project.

The agency says on the the website for the Connector that it "will ease traffic flow, decreasing the number of idling vehicles, conserving fuel, and reducing exhaust pollutants in alignment with Maine’s Climate Action Plan."

But even in isolation, this emissions benefit is typically "negligible at best," said Pérez. Despite ongoing improvements in vehicles' fuel efficiencies and even electrification, he said, studies show that more use of expanded roads tends to outweigh this benefit.

Pérez pointed to examples in the Washington, D.C. area, Salt Lake City and elsewhere where highway expansions that aimed to reduce gridlock instead led to more traffic and further need for expansions years later — a paradox known as "induced demand."

A 2015 paper from the University of California-Davis explains this phenomenon: "Adding capacity decreases travel time, in effect lowering the 'price' of driving; and when prices go down, the quantity of driving goes up," author Susan Handy wrote.

New roads, for instance, can encourage more low-density development, which in turn fills those roads with additional drivers. This counteracts the value of highway expansions in alleviating congestion, Handy said, and at least partly offsets the emissions reductions that come along with it.

Courtney, with the MTA, said "the Gorham Connector's design and goals suggest a different outcome," arguing that the project is unique as a limited-access highway without many intersections or entrances.

"By enhancing traffic efficiency and reducing congestion on local roads, it can offer a balanced approach that considers both transportation needs and environmental impacts," she said.

Portland resident Myles Smith, a steering committee member with Mainers for Smart Transportation, a volunteer group opposing the Gorham Connector, isn't convinced.

"It's part of a pattern of showing only the rosiest possible scenarios of how, theoretically, on paper, with a lot of other assumptions going perfectly, it might reduce climate emissions," he said. "It assumes a lot of other things that they have no control over at the Turnpike Authority, like land-use planning and public transportation."

New measures of climate impacts

The 2012 study backing the bypass proposal found that implementing a bevy of suggested road improvements and expansions, including the Connector, would decrease local vehicle hours traveled, or VHT — an analog for congestion, measuring how much time people spend in their cars, Pérez said — by about 10% versus 2035 projections.

It also said the area's vehicle miles traveled, or VMT — which measures how much people are driving overall — would increase relative to 2035 projections if the bypass was built, but would decrease in scenarios where only existing roads were improved, or where public transit was the focus.

"This is why we propose a 'three-legged stool' approach," Courtney said — one that also emphasizes dense development and increased public transit access, so that VMT increases might be offset by other benefits.

VMT is an increasingly common way to measure the climate benefits of transportation projects, Pérez said. Minnesota and Colorado have adopted new requirements toward goals for reducing their overall VMT, mandating that proposed road expansions either contribute to this decrease, or fund climate mitigation projects otherwise.

But advocates said VMT and VHT alone are not enough to measure the overall climate impacts of a project like the Gorham Connector. A more comprehensive analysis, they said, would include the environmental impacts of construction and would account in more detail for the role of the non-road improvements that the MTA is also calling for.

A need for coordinated solutions

The 2012 study, in its final recommendations, said all three strategies — changes to roads, transit and development patterns — would need to "work together to provide the desired results" for improving connectivity and reducing traffic impacts in the Portland area.

For example, more dense development and less congestion will make new transit approaches more viable, Courtney said.

The Turnpike Authority has little direct control over those kinds of reforms, but says on its website that it expects "other regional studies" in those areas to be part of the Gorham Connector planning process.

"The Gorham Connector project, combined with additional initiatives being considered by the MTA and Maine (Department of Transportation) — such as additional park-and-ride facilities, electric vehicle charging stations, and enhanced transit opportunities — will collectively contribute to reduced greenhouse gas emissions compared to a 'do nothing' scenario," Courtney said.

Smith said these other efforts are moving more slowly and with less state support than the Connector has received, putting these parallel solutions out of step with each other.

Maine is facing a lawsuit from youth climate activists over regulators' decision earlier this year not to adopt California's Advanced Clean Cars II rule, which would have ramped up requirements for electric and plug-in hybrid vehicle sales through model year 2032.

The state is still a long way off from the EV goals set in its 2020 climate action plan, which also aims to reduce light-duty vehicle miles traveled 10% by next year and 20% by 2030.

Advocates applauded a new emphasis on transit, biking, walking and other alternative strategies to achieve those VMT goals in the recommendations from a state climate council working group for a forthcoming update of the climate plan, due out in December.

It's an example of slow progress toward more holistic approaches to transportation and climate planning, which, Pérez said, must extend to technical details like the traffic models that underlie projects like the Gorham Connector in order to succeed.

"Those models need to think about what they're measuring — what matters most," he said. "The mindset is, 'we're designing for vehicles,' and that's what they're measuring for, not measuring for the movement of people."