A mileage-based road user charge would involve assessing owners of individual vehicles on a per-mile basis for the distance the vehicle is driven. Currently, federal highway and public transportation programs are funded mainly by motor fuel tax receipts that flow into the Highway Trust Fund (HTF). The tax rates, set on a per-gallon basis, have not been raised since 1993, and receipts have been insufficient to support the transportation programs authorised by Congress since FY2008. The long-term viability of motor fuels taxes is also questionable because of increasing vehicle fuel efficiency and the wider use of electric vehicles. Economists have favored the use of mileage-based user charges as an alternative to motor fuels taxes to support highway funding. This book examines considerations and viability of road user charges based on mileage.