Estimating the Equity Effects of Adding Additional Parameters to a Mileage-Based Road Usage Charge for Seven States

Abstract

This paper explores the feasibility and sensitivity of a mileage-based road usage charge (RUC) as an alternative to the gas tax. The specific purpose is to evaluate factors that could be considered when setting a charge to account for the complex makeup of statewide motor fleets, and to consider the diversity of household driving behaviors and experiences. The researchers considered a range of potential parameters before choosing to focus on fuel type and fuel efficiency. If based on annually adjusted efficiency quantiles, a parameterized RUC could prevent revenue erosion over time. Formulas based on these parameters were compared with the current fuel excise tax and a flat RUC. Distributional effects of parameters were assessed for urban, mixed, and rural household categories, and for vehicles of different fuel types. Results show that households in urban tracts tend to pay slightly more under all formulations, and households in mixed and rural tracts pay less compared with an excise-based gas tax. In addition to changes across regions of a state, the method allows examination of the groups within these categories. Research found that adjusting for fuel efficiency reduced the change in incidence between urban, mixed, and rural census tracts, and between fuel types, that results from moving to a flat RUC. Fuel type parameters resulted in only small differences from the flat rate RUC because of low alternative fuel penetration in most states. This may change over time depending on the rate of integration of alternative fuels into the passenger car fleet.