Despite concerns about the long-term solvency and sustainability of the federal highway trust fund, the Fixing America’s Surface Transportation or FAST Act passed by Congress in December 2015 did not include what many said was a much needed increase in the federal gas tax, which has remained unchanged since 1993. Congress instead offset a transfer of general funds to supplement gas tax revenues by tapping a Federal Reserve surplus fund among other sources. The action came at the end of a year in which eight states did raise their own gas taxes. With the fuel efficiency of the nation’s vehicle fleet improving and the greater adoption of electric vehicles on the horizon, some states are also looking to a new revenue mechanism that some believe could one day replace the gas tax—a mileage-based user fee. Concerns about how the fees would be administered and whether it could ever be done as efficiently as the gas tax are causing doubts it will be ready in time to help fund the next long-term iteration of the federal program when the FAST Act expires in 2020.