Trucks and other vehicles the U.S. Army is using in Iraq for troop and equipment transport are outdated and consume too much fuel, according to a study published by the National Academy of Sciences. The study, conducted by the academy's National Research Council at the Pentagon's request, proposed use of lighter metal alloys to improve the durability and performance of the military trucks. The report said high fuel consumption takes a financial and logistical toll on the Army and limits its agility. According to the report, fuel makes up 70% of the tonnage shipped to a battle zone, and one armored division alone consumes 600,000 gallons per day. The academy said improved fuel efficiency could reduce not only the amount of fuel transported but also the numbers of personnel and equipment needed to do so. The study recommends use of more modern high-strength steels to reduce weight without reducing protection, as well as aluminum and magnesium alloys to replace steel altogether in some components. The Army has a fleet of 250,000 trucks, ranging from the light-duty Humvee that replaced the Jeep to heavy-duty flatbed equipment transporters and tractor-trailer units, along with 110,000 trailers.