VEHICLE KILOMETERS TRAVELED: EVALUATION OF EXISTING DATA SOURCES

Vehicle kilometers traveled is the total kilometers traveled by motor vehicles on the highway system during a given period of time. Vehicle kilometers traveled by passenger automobile is an important variable in the analysis of fuel efficiency, fuel consumption, environmental quality, and highway safety. Changing patterns of future vehicle kilometers traveled have significant applications for energy conservation and economic stability. This report evaluates existing data sources for vehicle kilometers traveled and gasoline consumption. Collection, reporting, consolidation, and estimation procedures are addressed. Since direct measurement of vehicle kilometers traveled has never been made, the available information consists of indirect estimates based on various sets of assumptions. The type of assumptions and the reliability of the data determine the models and types of hypotheses that can be meaningfully tested. Historically, the importance of vehicle kilometers traveled accumulation has been directed toward highway planning and included such areas as traffic density, highway safety, and other non-energy-related areas. For these nonenergy endeavors, the traffic-counting methodology has been the procedure used most widely by the individual states to estimate vehicle kilometers traveled. However, since the 1973 energy crisis, the Federal Highway Administration has requested that the states estimate vehicle kilometers traveled based on average fuel efficiency rated for different vehicle classifications. This alternative methodology may be a more appropriate way in which to solve energy-related issues because energy efficiency is one of the predetermined variables. However, fuel-consumption rates involve many heterogeneous imputs, and it has been difficult to arrive at a meaningful state average for fuel economy. The Federal Highway Administration has not developed and selected one specific methodology to estimate vehicle kilometers traveled. No single procedure has been established to collect, report, and consolidate vehicle kilometers traveled data. Each state and every region within a state selectes its own process for gathering these data. Therefore, an accurate and reliable estimate of vehicle kilometers traveled from heterogeneous inputs cannot be obtained. /Author/