The federal government’s surface transportation programs are financed mostly through the Highway Trust Fund, which has two accounts, one for highways and one for mass transit. The fund records inflows from revenues collected through excise taxes on the sale of motor fuels, trucks and trailers, and truck tires; taxes on the use of certain kinds of vehicles; and interest credited to the fund. It records cash outflows for spending on designated highway and mass transit projects, which is mostly in the form of grants to state and local governments. Most of the authority to spend is controlled by limitations on obligations contained in appropriation acts. Since 2001, that spending has exceeded the revenues from fuel and other taxes that are credited to the Highway Trust Fund for highway programs.

This document presents CBO’s projections of the two trust fund accounts’ finances over the next 10 years.