Sport-utility vehicles have become icons of American consumption in the past decade, changing the look of the nation's highways. But few consumer products have attracted such adulation and scorn. Fans of the trucklike passenger vehicles love their spacious interiors, rugged appearance and high-off-the-ground seating. Critics see them as gas-guzzling, turnover-prone behemoths that spew pollutants and endanger the occupants of smaller cars. Like minivans, SUVs are categorized by the government as light trucks, which are held to less stringent fuel-efficiency and safety standards than cars. The Bush administration has ordered automakers to increase light-truck mileage efficiency by a total of 1.5 mpg — to 22.2 mpg — during the 2005-2007 model years. But environmentalists say that's not enough.