In a significant step the administration of United States President Barack Obama has finally standardised major new fuel efficiency rules for cars and light trucks.
Under the new rules the fuel efficiency of these vehicles will nearly double by 2025.
The rule, strongly opposed by Republicans and some carmakers, builds on the standard for vehicles for model years 2011-2016, which requires carmakers to raise average fuel efficiency to 6.6l/100km.
The new standards cover vehicles with model years 2017 to 2025.
The rules are the result of more than a year of negotiations between the administration, carmakers and environmental groups.
“These fuel standards represent the single most important step we’ve ever taken to reduce our dependence on foreign oil,” President Obama said in a statement.
Mr Obama’s challenger in the presidential race, Mitt Romney, sharply criticised the rule.
“Governor Romney opposes the extreme standards that President Obama has imposed, which will limit the choices available to American families,” spokeswoman Andrea Saul said.
The US Environmental Protection Agency and the National Highway Safety Administration will conduct a mid-term evaluation of the standards to determine if they are effective and whether they need adjustment.
The standard is based on one set by California, which played an “integral” role in developing the national program, the White House said.
Carmakers and unions were largely supportive of the announcement, saying it brings greater regulatory certainty.
US Transportation Secretary Ray LaHood said the new standards would raise the average cost of buying a car by $1800 by 2025 but said the fuel savings “far outweigh the increase in the cost of an automobile.”
Fuel savings will be $8000 over the life of a car, according to the administration.