WASHINGTON — Newly appointed U.S. Transportation Secretary Sean Duffy has ordered a rewrite of stringent federal fuel economy rules for cars that were enacted by former President Joe Biden.

The memorandum signed by Duffy shortly after he was sworn into office Tuesday directs the National Highway Traffic Safety Administration to immediately initiate “a rulemaking to rescind or replace all existing CAFE standards,” according to the transportation department.

The reversal would undo a rule put in place by the Biden administration that requires carmakers to reach an average of 50.4 miles per gallon across their fleets by the 2031 model year, under a final rule announced in June 2024.

The effort is part of a broader Trump administration push to undo regulations put in place by Biden, especially ones related to climate and other environmental issues.

The move also comes as the Trump administration seeks to undo Biden’s efforts to speed the nation’s transition to cleaner zero-emission vehicles, which Trump has blasted as an “EV mandate.”

Automakers have invested billions of dollars in new EV models and factories to meet the Biden-era requirements — and take advantage of generous EV subsidies available under Biden’s signature Inflation Reduction Act law that was passed in 2022 and that Trump has promised to repeal.

However, many carmakers have dialed back ambitious electric-vehicle plans amid a slowdown in demand and steep losses on plug-in vehicle sales. Some industry executives have criticized the Biden-era policies for getting ahead of consumer appetite for EVs.

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