The increases had been set up by a collaboration between California and former President Barack Obama's regulators as a way to. Thirteen other states and the District of Columbia also follow California's emission standards.
Public hearings on the proposals have drawn mainly opponents, including scientists and health officials who say the change would throw out bedrock public-health studies that draw on confidential data on individual patients.
The Obama administration had proposed a tougher standard requiring a corporate average fuel economy of 54.5 mpg, which in real world numbers is closer to the low 40 mpg range, a number automakers have said they can meet.
If the Trump administration challenges California's long-standing latitude to set its own emissions rules, it would be wading into untested legal waters, said Deborah Sivas, a law professor and expert on the Clean Air Act at Stanford University.
The move is expected as early as Thursday and will propose revoking California's power to set state vehicle emissions rules and mandate the purchase of electric vehicles, a government official briefed on the matter said and was reported by Reuters. The automakers say the California Air Resources Board rules for vehicle model years 2022-2025 are onerous and impractical, despite a CARB analysis in 2017 concluding that the standards are technologically feasible. "Importantly, we also seek the reinstatement of flexibilities that exist in the regulation today but that are mostly phased-out by 2021". While an attack on California's clean auto mandate will cause some uncertainty, it's unlikely to derail the influx of electric vehicles poised for release over the next several years by an increasingly long list of automakers that includes Ford, VW and Porsche. Whether this would be enforceable at a federal level, isn't entirely clear but in practice, it would likely mean very little given that the bulk of major automakers have already invested in EV technology.
Trump will seek to revoke California's authority to regulate automobile emissions, including its mandate for electric vehicle sales. But instead of pursuing a deal, the plan spearheaded by the Transportation Department and the Environmental Protection Agency will attempt to eliminate or override California's emissions authority and force the state to adopt less-stringent federal pollution standards. Fifteen states use this rule to implement California's standards within their own borders.
Representative Jimmy Gomez, a California Democrat, posted on Twitter that the state's "vehicle emissions standards are a big part of our environmental identity". Stay out of CA's way! The science behind the forecast is unclear.
The administration projects the new rule would reduce "societal costs" by about $500 billion over the life of the vehicles, but the administration's overall forecast net benefits are unclear, once higher fuel consumption is taken into account.
In January, California Governor Jerry Brown set a new target of 5 million zero-emission vehicles in California by 2030, up from a prior goal of 1.5 million by 2025. Agencies are expected to claim it will reduce traffic fatalities by making it cheaper for drivers to replace older, less-safe cars, while paring sticker prices for new vehicles even if motorists have to spend more for gasoline.