The Obama administration has raised fuel economy standards for trucks in the United States in a bid to cut greenhouse gas emissions and reduce dependence on fossil fuels between now and 2027. The rules announced Tuesday cover heavy- and medium-duty vehicles including school buses, delivery vans, garbage trucks and large long-haul tractor trailers. Heavy vehicles represent just 5 percent of road traffic, but consume 20 percent of the motor fuel burned in the nation. Supporters of the new initiative say that when fully implemented, the rules will save about 319 billion liters of fuel a year, cut $170 billion in fuel costs, and keep more than one billion tons of carbon pollution out of the air. Experts estimate that large trucks typically burn 76,000 liters of fuel a year. The new measures follow earlier efforts to improve energy efficiency for cars, aircraft, power plants and air conditioners. The Consumer Federation of America said the new efficiency standards will make it less expensive for trucks to deliver their cargo, making many goods cheaper for consumers. Leaders of the American Trucking Associations said they were "cautiously optimistic" that the new rules will achieve their goals without unduly disrupting operations. The ATA welcomed the time given to manufacturers and the industry to meet the new standards.