From the LA Times U.S. highway trust fund veers toward crisis
"As motorists cut back on their driving and buy more fuel-efficient cars, the government is taking in less money from the federal gasoline tax.
The result: The principal source of funding for highway projects will soon hit a big financial pothole. The federal highway trust fund could be in the red by $3.2 billion or more next year."
This was not unpredictable, and the response is likely to be an increase in the gas tax at the next surface transportation authorization, which will further drive motorists from gasoline.