NTV Road data are based on statistics compiled by the Federal Highway Administration (FHWA) at the U.S. Department of Transportation from reports submitted by the states. In 1995, FHWA revised the data series for the number of U.S. road vehicles. The new categories include passenger car, light trucks (“other 2-axle, 4-tire vehicles”), “single-unit 2-axle 6-tire or more truck” and combination truck tractors. Pre-1993 data were assigned to the closest available category. Data for light trucks or “other 2-axle, 4-tire vehicles” include vans, pick-up trucks and sport utility vehicles. “Single-unit 2-axle 6-tire or more trucks” are on a single frame with at least two axles and six tires, and correspond to the category of single-unit trucks. Combination
