For the first 50 years of the Highway Trust Fund (HTF), user fees were sufficient to fund the federal portion of building and maintaining the nation’s transportation system. Limiting fees to actual users of services is seen as a more equitable approach than paying for transportation out of the general fund. For the past decade, however, user fee income to the HTF has not kept pace with federal authorization levels, and Congress has not taken action to increase the level of user fees or decrease federal authorizations to bring the fund’s obligations and revenues into balance.