Rob Atkinson particpated in a an expert Q&A panel on VMT fee transition and implementation hosted by the Bipartisan Policy Center. Funding for the Highway Trust Fund comes mostly from the federal tax on gas paid by drivers at the pump, which has not changed from 18.3 cents per gallon since 1993. As consumers drive more fuel-efficient vehicles, less revenue is flowing into the fund, which forces Congress to periodically bail it out—generally with unrelated revenues or deficit spending. To sustainably pay for Highway Trust Fund programs, BPC previously recommended that Congress raise the gas tax and transition to a vehicle miles traveled fee, or VMT, charging consumers for each mile they travel. Yet there are key questions – including an array of technical, institutional, and political challenges – about how best to facilitate that transition and implement a national VMT.