Calls for a federal gas tax hike are rising in the wake of historically low gas prices and a May 2015 deadline to fix funding for the Highway Trust Fund. Without reform, the Highway Trust Fund, which relies heavily on the federal gas tax, will become insolvent, forcing the Department of Transportation to cut funding for state infrastructure projects.

One of the few proposals to solve the Highway Trust Fund’s long-term funding problem comes from Sen. Bob Corker, R-Tenn., and Sen. Chris Murphy, D-Conn. During last year’s Highway Trust Fund debate, Corker and Murphy proposed a 12 cents per gallon increase in the gas tax spread out over two years, then linking the tax to inflation. In order to make the tax hike more acceptable for Republicans, the proposal made some temporary tax breaks permanent so that the legislation would technically be revenue-neutral.