President Donald Trump and federal officials on Thursday formally proposed scaling back Obama-era regulations for fuel economy and cited safety concerns that lighter, more fuel-efficient cars would be more dangerous on American roadways.

The 978-page proposal outlines federal guidelines to freeze emissions standards at 2020 levels and potentially sets up a showdown with states over long-running rules that let California and 13 other states adopt more stringent pollution standards.

California and 16 other states have already launched a preemptive lawsuit in case the Trump administration rolled back the policy.

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The document pivots the Obama administration's push for cleaner vehicles and less pollution toward safety. Although the proposal is nearly 1,000 pages, it's aim is made clear within the first few words in its title: “Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021-2026 Passenger Cars and Light Trucks."

Under the old rule, the Trump administration claims, automakers would choose low-cost, less-safe ways to lightweight vehicles.

"Additionally, in light of the reality that vehicle manufacturers may choose the relatively cost-effective technology option of vehicle lightweighting for a wide array of vehicles and not just the largest and heaviest, it is now recognized that as the stringency of standards increases, so does the likelihood that higher stringency will increase on-road fatalities. As it turns out, there is no such thing as a free lunch," the administration wrote.

EPA Acting Administrator Andrew Wheeler

EPA Acting Administrator Andrew Wheeler

The standards would freeze fleet fuel economy standards around 37 mpg in real-world fuel economy.

The proposal also says that fuel-saving features such as turbocharging and dual-clutch transmissions haven't been as effective at improving fuel economy as expected nor have they been widely accepted by consumers.

Critics have largely already dismissed the plan as a political ploy and say that the existing standards have not diminished safety.

"The Trump administration is driving our auto future in reverse," the Natural Resources Defense Council said in a statement. "The clean car standards are already saving our families billions at the pump, supporting nearly 300,000 American jobs, and cleaning up dangerous tailpipe pollution. We need to speed up that progress, not slide backward. Let’s keep our eyes on the road—and not let Trump and his dirty deputies run us into the ditch."

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Even the conservative Securing America's Future Energy organization (ironically also named SAFE) railed against the rollback.

"The federal government’s own data shows that when managed properly for vehicle footprints, lightweighting and fuel economy rules don’t undermine highway safety," said CEO Robbie Diamond, in a statement emailed to Green Car Reports. "Implementing policies that will result in such a dramatic increase in gasoline demand ignores the lessons we have learned time and again about the consequences of our oil dependence—it hurts American families and businesses, it burdens our armed forces, it boosts the trade deficit, makes our automotive industry less competitive, and continues the wealth transfer to petrostates who manipulate the oil market. Gasoline demand in every other OECD member country is declining and they are getting more economic output out of every barrel they consume. America must do the same if we wish to remain prosperous and secure."

Other critics of Trump's plan said it lacks scientific foundation.

"Millions of vehicle owners, transportation experts, public health officials and consumer advocates are rightfully outraged. Multiple polls show an overwhelming majority of Americans favor clean car standards because no matter what size car or truck they buy, drivers want more efficient, cleaner vehicles. The current standards were created in collaboration with California and the entire automotive industry and have directly made new cars and trucks cleaner and cheaper to drive. EPA and California Air Resources Board scientists spent years studying the standards, as was required, and concluded last year they are technologically feasible and cost-effective. New cars and trucks aren’t cleaner and more efficient by accident or because of automakers’ goodwill. They are more efficient because forward-looking and scientifically sound public policies require them to be," Don Anair, deputy director of the clean vehicles program at the Union of Concerned Scientists, said in a statement.

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The SAFE proposal also proposes to withdraw California's waiver that allows the state to set its own emissions standards, which has led to mandates that automakers build zero-emissions cars and sell them in California and other states.

"The (Clean Air Act) gives EPA the authority to waive preemption for California under certain circumstances," the proposal states. "(The Energy Policy and Conservation Act) does not provide for a waiver of preemption under any circumstances. In short, the agencies propose to maintain one national standard — a standard that is set exclusively by the Federal government."

The Energy Policy and Conservation Act of 1975 formed the NHTSA and gave it control over fuel-economy standards. This provision is what prompted the 17 states to sue the EPA in May. 

The proposal will be open for comment for 60 days. After that, its outcome is likely to be tied up in courts for years.