A University of Michigan researcher says American households without a vehicle have increased nearly every year since 2007, providing further evidence that motorization may have peaked in the United States. Michael Sivak of the U-M Transportation Research Institute followed up his research from last year showing that Americans own fewer light-duty vehicles per household, drive them less and consume less fuel than in the past. He examined recent trends in the proportion of U.S. households without a car, pickup truck, SUV or minivan. Sivak found that 9.2% of U.S. households were without a vehicle in 2012, up from 8.7% in 2007.