National Evaluation of Mileage-Based Charges for Drivers

This paper presents initial results and conclusions from the National Evaluation of a Mileage-Based Road User Charge, a 2-year field study conducted by the University of Iowa Public Policy Center. The study, which evaluates technical feasibility and user acceptance of mileage-based charging as a potential replacement for the current motor fuel tax, was authorized by the "2005 Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users," which reauthorized federal transportation funding.

This study is the first to examine road user charges on a national and multijurisdictional scale. Approximately 2,650 volunteers from 12 areas throughout the country participated in the study, which concluded in July 2010. The system mileage charges were totaled and apportioned to the federal, state, and local levels with the use of onboard computers installed in participants' vehicles. The onboard computers contained Global Positioning System (GPS) receivers with an associated geographic database to identify the taxing jurisdictions in which the vehicles traveled. The average participant drove approximately 9,000 mi during the study (the study totaled more than 21 million miles).

Approximately 92.5 percent of all driven miles were successfully measured by both the GPS and the onboard diagnostics system (OBD-II). Of the miles driven without GPS, 6.9 percent could be reliably assigned to jurisdictions by using straightforward interpolation techniques. Approximately 0.6 percent of total miles driven could not be reliably assigned to a state or local jurisdiction. Participant attitudes regarding the system and the overall concept of mileage-based charging were assessed. At the end of the study, 71 percent had a highly or somewhat positive view, and 17 percent held a highly or somewhat negative view. Participants consistently (but to varying degrees) preferred audit ability, which consisted of receiving detailed monthly invoices, over maximum privacy protection.