EXCESS TRAVEL: CAUSES, EXTENT, AND CONSEQUENCES

The amount of excess travel in the United States is estimated on the basis of past research and new empirical studies. Excess travel is defined as the arithmetic difference between total actual highway use, exclusive of destination-free "pleasure" driving, and the use that would have resulted if all such travel had been made by using the optimum route connecting each individual origin-destination pair. Excess travel is shown to be caused by a number of different factors acting singly or in combination. These include route selection criteria and efficiencies in necessary route-planning information, in the highway information system, and in both route-planning and route-following skills. The synthesis of all available data indicates that excess travel contributes 4 percent of all vehicle miles of travel and 7 percent of all travel time for work-related trips. Corresponding figures for non-work-related trips are 20 and 40 percent, respectively. Applying these proportions to total U.S. travel results in a total of excess travel amounting to 83.5 billion mi and 914,000 person-years per year at a total estimated cost of more than $45 billion.