Federal spending on highways does not correspond very well with how the roads are used. “CBO examines three approaches lawmakers could consider to make highway spending more productive: “Federal spending on highways (or, synonymously, roads) totaled $46 billion in 2014, roughly a quarter of total public spending on highways. About 95 percent of that amount was spent for the construction of highways or for their improvement, expansion, and major repair, and the remainder was spent for operation and maintenance. Recently, two factors have combined to highlight the importance of making each dollar spent on federal highway programs more productive economically. First, the federal government’s main source of funds for highways—gasoline tax revenues dedicated to the Highway Trust Fund—has been insufficient to pay for federal spending on highways. Since 2008, lawmakers have transferred about $143 billion from other sources to maintain a positive balance in the trust fund. Second, adjusted for changes in construction costs, total federal spending on highways buys less now than at any time since the early 1990s.”