The Trump administration unveiled lower fuel economy standards, reducing the U.S. vehicle fleet’s 2031 target by about 15 miles per gallon and reversing a key Biden administration effort to promote more efficient and electric vehicles. The regulations, first proposed in December, are presented as an affordability measure that will lower vehicle prices by about $1,300 on average and support Detroit automakers. The rollback also underscores the administration’s move away from federal policies encouraging drivers to shift from gasoline vehicles to electric cars and trucks, while opponents say weaker standards could raise gasoline expenses.