The Transportation Department’s Federal Highway Administration on Thursday proposed a rule that would require states to track on-road carbon dioxide emissions and set reduction goals aimed at achieving net zero emissions by 2050.

However, critics of the proposal quickly pointed to last week’s Supreme Court ruling limiting EPA’s climate authority over power plants, arguing that the same legal reasoning would indicate the climate goals being proposed are beyond FHWA’s authority.

Background: Several Obama-era laws authorized FHWA to set new performance management measures for the nation's highway system. Prior rules required state and metropolitan authorities to assess and report various metrics on highway safety, road and bridge infrastructure and system performance such as traffic congestion and on-road emissions of conventional pollutants.

The Obama administration also established a greenhouse gas performance measure, but the Trump administration repealed it.

On-road carbon dioxide emissions make up over 80 percent of emissions in the transportation sector, the biggest U.S. contributor to greenhouse gases.

Details: The agency says it has reconsidered and believes the sector's contribution to climate change and its harmful effects on transportation infrastructure justify the performance measures.

It would require state and metropolitan authorities to track emissions and to establish "declining targets" to reduce CO2 emissions from on-road sources relative to 2021 with an eye toward reaching an economy-wide net zero goal by 2050.

“State DOTs and [metropolitan planning organizations] would have the flexibility to set targets that work for their respective climate change policies and other policy priorities, so long as they are in line with the net-zero goals by 2050 set forth in this rule,” the rule reads. “The proposed rule also would require State DOTs and MPOs to report on their progress in meeting the targets.”

The rule would cost up to $12.9 million a year over the first decade, FHWA estimated. It did not quantify the benefits “because they are difficult to forecast and monetize,” but calculated that breaking even would require reductions of up to 984,000 tons over the next decade, or 0.006 percent of total transportation sector emissions.

Reaction: Environmental groups quickly praised the proposal.

“By measuring emissions and developing plans to cut them, states and localities can determine how to build a resilient and efficient transportation system that will serve us all for decades to come,” said Deron Lovaas, a senior advocate at the Natural Resources Defense Council.

“We know what’s needed to reduce these emissions,” said Lisa Frank, executive director of Environment America’s Washington Legislative Office. She urged states to expand public transit and emphasize walking and biking, and to install electric vehicle charging stations.

But Republicans and transportation industry groups pounced on the proposal as overreach, especially in light of the recent Supreme Court decision.

This regulation was not one of the transportation resiliency measures included in last year's bipartisan infrastructure package, EPW ranking member Shelley Moore Capito (R-W.Va.) said. “Unfortunately, this action follows a common theme by both DOT and the administration, which is implementing partisan policy priorities they wish had been included in the bipartisan bill that the president signed into law,” she said.

Nick Goldstein, vice president of regulatory and legal issues at the American Road and Transportation Builders Association, said that at first glance the proposal appears similar to the Obama-era rule they opposed and that was repealed.

He also argued that it runs afoul of the standard set by the Supreme Court last week in its ruling limiting EPA’s authority over power plant carbon dioxide emissions. That ruling said EPA’s sweeping Clean Power Plan had strayed too far into energy policy overseen by other agencies.

“Here, the Department of Transportation is swinging into the EPA space,” Goldstein said. “And I think what West Virginia v. EPA tried to do is say that agencies need to stay in their lane as established by Congress. And I think our initial concern with this rule is that it's outside of FHWA’s lane.”

What’s next: Comment on the proposal, Reg. 2125-AF99, will be open for 90 days after publication in the Federal Register, which FHWA said it expects to happen next week.