Traffic counts on about of half of the 47,000 miles of Interstate highways in the U.S. are 40,000 daily trips or more. At a toll of 10 cents per mile for cars (the NJ Turnpike charges 11.4 cents), and 30 cents for trucks, those high-traffic segments could be self-supporting on a life-cycle basis, according to Jordi Graells, CEO of Abertis USA.