California has had the authority under the half-century-old Clean Air Act to set its own mileage standards to combat its chronic smog problem.
The administration also contends that hiking US oil consumption by 2 to 3 percent over forecast levels would have a minimal impact on the environment, boosting global average temperature by just "3/1000th of a degree Celsius by 2100". A dozen other states and Washington DC also follow higher standards. Under the Obama plan, the fleetwide fuel economy would have risen gradually to roughly 47 mpg by 2025.
But Becerra, the California attorney general, said the EPA is rewriting its own detailed analysis from 2012 and that his state is set to exceed its goal of electric vehicles.
About a third of these projected savings, or $198 billion, are tied to the agencies' assertion that, by slowing pace at which new vehicles get more expensive, they'll allow people to replace older and less-safe cars more rapidly.
The state's Democrats in Washington and Sacramento have come out aggressively against the proposal. Gov. They said the average cost of a new automobile is $35,000 and attributed part of that to increasing fuel standards.
Two former EPA mileage officials said the administration's proposal departed from years of findings on fuel efficiency, vehicle safety, exhaust emissions and costs.
"We strongly oppose the Trump administration plan to roll back these clean-car standards, and we're going to fight to do that", Shapiro said in a conference call with the attorneys general of California, Xavier Becerra, and Massachusetts, Maura Healey. "It means that the federal government will have slightly less control over the kinds of cars and trucks people can buy".
The soaring prices of cars have led more Americans to hold off on new auto purchases.
Public health experts and environmental groups condemned the White House proposal even before its official release, arguing that it overlooks how much money Americans would save at the pump if cars were more efficient and also squanders a chance to cut pollution from the transportation sector, which has become the nation's largest source of carbon dioxide emissions. Mui assumes that real world driving would result in about 80 percent of the fuel efficiency measured in laboratory testing.
Heidi King, deputy administrator of the National Highway Traffic Safety Administration, said the freeze would reduce highway deaths by 1,000 per year "by reducing these barriers that prevent consumers from getting into the newer, safer, cleaner, more fuel-efficient cars".
A 60-day comment period will begin once the proposal is published in the Federal Register, and a final rule could be finalized by the end of 2018 or early next year.
The Obama administration had planned to keep toughening fuel requirements through 2026, saying those and other regulations on vehicles would save 40,000 lives annually through cleaner air.
"Rolling back these successful rules is a serious mistake that will cost consumers dearly". "The Trump administration has launched a brazen attack, no matter how it is cloaked, on our nation's clean auto standards", Becerra said on Twitter.