The agreement between the California Air Resources Board and the automakers — Ford, Honda, Volkswagen and BMW — covers about 30% of new cars and SUVs sold in the United States. It presents a direct challenge to the Trump administration’s plans, expected to be formally announced later this summer, to roll back tougher tailpipe pollution standards put in place under President Obama.
The fuel efficiency rules are key to reducing U.S. emissions of carbon dioxide and other gases that contribute to global warming. Cars, trucks and other forms of transportation are the biggest source of U.S. emissions, accounting for about 30% of the total.