New Hampshire Gov. Chris Sununu already says he won't commit New Hampshire to joining the program, known as the Transportation and Climate Initiative, or TCI. Maine and Vermont have also held off committing to the program, citing concerns about impacts to rural drivers. Governors of many other participating states, including Massachusetts and Rhode Island, have voiced support for the program.

TCI would limit and price emissions from vehicle fuel distributors. Revenues from that price would be reinvested by the states – as they are under the Regional Greenhouse Gas Initiative that caps and prices emissions from power plants in the Northeast.

New models released Tuesday with a draft “memorandum of understanding” for the TCI program say it could generate $2 to 7 billion in revenue for road and clean transit programs for the states involved – along with major public health savings.

But the modeling also suggests that even with total buy-in from the states that have participated in the planning process, the program would have to be as ambitious as possible to cut transportation emissions significantly over where they would be anyway by the early 2030s.

New Hampshire has joined 11 other states and D.C. in the TCI planning process, but getting those jurisdictions to agree on adopting that ambitious version of the plan was never guaranteed.

The new TCI models also say it could add up to 17 cents on the gallon to fuel prices for drivers – though it’s not clear yet if or how fuel distributors would choose to pass on the program’s costs to customers.

In a statement issued just hours after the draft of the program went out for public comment, Sununu said it won't decrease emissions enough to justify the potential increased costs for drivers.

“New Hampshire is already taking substantial steps to curb our carbon emissions," Sununu says. "This program is a financial boondoggle and the people of New Hampshire will never support it.”

Sununu's office provided comment from the Department of Environmental Services suggesting that New Hampshire will remain a part of the TCI planning process. 

Environmental advocates have urged Sununu to support the program.

"The governor’s response is premature and disappointing," says Roger Stephenson, a Stratham resident and the regional advocacy director for the Union of Concerned Scientists. "He ought to encourage citizens to weigh in on the framework."

And state Sen. David Watters, a Democrat from Dover, says he plans to propose a legislative commission to study the costs and benefits of joining it next spring.

He says it could be worthwhile for the revenue it would generate.

"We could use this money for road improvements and signal improvements, which are low-hanging fruit for increased energy efficiency, but also buses and school buses," he says.

Watters says he also hopes to study the potential effects of not joining the program.

“If the states around us pass it, we may see those increases in fuel prices at the distribution level anyways and not benefit at all from it,” he says.

The program would be finalized next year – beginning with a public comment period that closes Feb. 28. The states would decide whether to adopt the program during their 2021 legislative sessions, before the final version launches in 2022.

This story comes from the New England News Collaborative, eight public media companies, including The Public's Radio, coming together to tell the story of a changing region, with support from the Corporation for Public Broadcasting.