An excellent Subsidyscope item reveals that, contrary to myth, highways are not financed by user fees but rather just like intercity rail and mass transit are subsidized by other financial flows:
Using Federal Highway Administration statistics, Subsidyscope has calculated that in 2007, 51 percent of the nation’s $193 billion set aside for highway construction and maintenance was generated through user fees—down from 10 years earlier when user fees made up 61 percent of total spending on roads. The rest came from other sources, including revenue generated by income, sales and property taxes, as well as bond issues. Going back further, the trend is more pronounced. Forty years ago, user fees amounted to 71 percent of revenues spent on roads.
I look forward to people explaining that highway travel may work in Europe, but that the United States isn’t populated nearly densely enough to make it viable as a mode of transportation.