An analysis of data from 20 years (1977 – 1997) of the quinquennial Vehicle Inventory and Use Survey (VIUS), collected by the U.S. Census Bureau, indicates that the overall population of heavy freight vehicles grew at the same rate as real GDP, just under 3% per year. However, the total miles operated by vehicles of this type grew 50% more, 4.5%, which produced a very large cumulative increase, from 46.8 billion miles in 1977 to 111.6 billion in 1997. This was because of a 34% increase in the intensity of use of heavy freight vehicles, as measured by changes in their average annual miles of operation. The key patterns underlying these aggregate changes are analyzed by examining the trajectories of several subdivisions within trucking over the period, segregating the data by private versus for-hire carriage and geographic range of service. There are a number of interesting nuances, but the main underlying trend is a sharp increase in the specialization of for-hire carriage in long-haul operations, complemented by an increasing relative dominance of private carriage in local operations.
