A letter report issued by the Government Accountability Office with an abstract that begins "Mileage-based user fee initiatives in the United States and abroad show that such fees can lead to more equitable and efficient use of roadways by charging drivers based on their actual road use and by providing pricing incentives to reduce road use. Mileage fees for passenger vehicles, however, continue to face significant public concerns related to privacy as well as cost challenges. Privacy concerns are particularly acute when Global Positioning System (GPS) units are used to track the location of passenger vehicles. Reliable cost estimates for mileage fee systems are not available, but implementing a system to collect fees from 230 million U.S. ...