The mileage-based user fee (MBUF) is a leading alternative to the gasoline tax. Instead of taxing gasoline consumption, the MBUF would directly tax drivers based on their vehicle miles traveled (VMT). The author estimates changes in annual household demand for VMT in response to changes in the cost of driving that result from adopting various MBUF alternatives, and finds that a flat-rate MBUF would be no more or less regressive than fuel taxes, now or in the future. The findings suggest that equity considerations based on ability to pay would not be a significant reason to oppose or support the adoption of MBUFs. While the equity implications of MBUFs are minimal, some groups, especially rural states, may find that the potential equity benefits of MBUFs could be overwhelmed by an increase in the tax rate to cover the higher costs of collecting and administering them. Concerns about the impacts of flat-rate MBUFs on vehicle fuel efficiency and greenhouse gas emissions are valid, but, at current oil prices, the tax rate is a small percentage of the total cost of gasoline. However, it is possible to structure an MBUF that provides incentives for fuel efficiency while maintaining the other favorable qualities of MBUFs, such as their economic efficiency and fiscal sustainability.
