Earler this year, Kenworth hosted a group of trucking editors for a ride and drive at the Paccar technical center near Mt. Vernon, Wash., in an area known as the Skagit Valley. The center has twin mile-and-a-half tracks. The outer loop is a 1/6-mile, two-lane, high-speed track used for testing aerodynamics and fuel economy. The inner 1.5-mile durability track simulates 1 million miles in three months.