The 12 states that belong to a coalition looking to reduce greenhouse gas emissions from transportation released a plan Tuesday for a regional “cap and invest” program.

The group of Northeast and Mid-Atlantic states, as well as Washington, D.C., are seeking comments on the plan, known as the Transportation and Climate Initiative, through the end of February.

Gov. Phil Scott and other state leaders will have to decide whether to sign onto the plan this spring.

Scott, a Republican, said that he believes the Green Mountain State needs to have a seat at the TCI negotiating table but that he will not support it if it’s “just a carbon tax.”

Meanwhile, New Hampshire Gov. Chris Sununu attacked the proposal this week.

The two-term Republican released a statement Tuesday afternoon calling TCI a gas tax in disguise that would “subsidize other state’s crumbling infrastructure.”

Sununu said New Hampshire will not participate in the program if it is created.

TCI would set a regional carbon dioxide emissions cap at current emissions levels. That cap would then decline over time to an undetermined level.

Regional fuel importers would buy emissions allowances at auction based on how much on-road gasoline and diesel they sell in each state.

States would then spend the auction proceeds on pollution-reducing measures such as public transit, making downtowns more walkable and electric vehicle incentives.

“In the long term, it’s what our communities look like and how they’re organized that … details what sort of transportation services we need,” said Peter Walke, deputy secretary of the Vermont Agency of Natural Resources, who is heading the state’s TCI team.

While key details, such as the regional emissions cap, are still being ironed out, the group modeled the costs and benefits of a 20-25% reduction by 2032.

Those models predict fuel prices could rise seven cents from TCI under a 20% reduction scenario, 14 cents under a 22% reduction and 17 cents under a 25% reduction.

Although Vermont has aggressive greenhouse gas emissions goals on the books, emissions have increased in recent years.

The state’s most recent data from 2015 show emissions are 16% higher than in 1990. Transportation accounts for 43% of the state’s emissions.

In New Hampshire, transportation accounted for 42% of greenhouse gas emissions, by far the largest source in the state, according to 2015 data in the New Hampshire Greenhouse Gas Emissions Inventory.

A new U.N. report said keeping global warming below 1.5 degrees Celsius would require a 55% reduction in emissions by 2030.

The “assumption that we’ve been operating under” for modeling purposes is that all of the costs will be passed on at the pump, Walke said, adding that this did not occur under the Regional Greenhouse Gas Initiative, the power sector cap and invest program.

Greenhouse gas emissions in the power sector were reduced by 40% over the past decade in RGGI’s nine member states.

The program was a small part of the market factors influencing power prices and the “same thing could happen in the fuel market” if distributors decide to absorb the costs rather than slightly increasing prices for customers, Walke said.

The TCI modeling also found that a 25% decrease in emissions would lead to an estimated 1,014 fewer air pollution related deaths and a half a percent increase in GDP, or gross domestic product, compared with “business as usual,” or a 19% emissions reduction.

Material from the Concord Monitor was used in this report.