Gas tanks in Tennessee may remain full for longer periods of time thanks to the availability of fuel-efficient vehicles, but the glass is half-empty when it comes to declining gas tax revenue. Federal transportation dollars are down, and the federal Highway Trust Fund is set to run out at the end of May. Susan Mattison, a research analyst for the State Comptroller’s Office of Research and Education Accountability, recently conducted a study of Tennessee’s fuel tax revenue. “Our taxes have become stagnant,” she says. “Unless something is done, they will not fund our transportation needs over time.” State leaders recently opted to delay debate on raising the state’s relatively low gas tax, despite the findings of the State Comptroller’s study. The U.S. Transportation Secretary was recently quoted as saying that Congress was close to reaching an agreement on long-term infrastructure funding at the federal level. The federal government typically spends $50 billion annually on infrastructure, but revenue from the federal gas tax brings in $34 billion of that amount. David Goldberg with the Washington, D.C.-based organization Transportation for America says the shortfall is making it hard to compensate for delayed projects in the wake of the Great Recession. “There’s a big backlog of maintenance and a pent-up demand for new transportation projects to deal with population growth in places like Nashville, which has been growing a great deal,” says Goldberg. Mattison says while Tennesseans may be reluctant to pay more at the pump in taxes, the funding is necessary to maintain a daily need for the population. “It’s important we have sufficient highway revenues,” she says. “Those fund the maintenance of existing highways, as well as construction of new roads that meet the demands of the population growth and the economic development of the state.” One alternative discussed as a way to collect taxes on the use of roads is a per-mile tax that could be calculated using current technology available in cars. President Obama is also promoting his GROW America Act, which would provide financial funding to states to establish long-term transportation plans, instead of relying on fluctuating funding.