The Moving Ahead for Progress in the 21st Century Act (MAP-21; P.L. 112-141), a two-year authorization of federal spending on highway and public transportation programs, surface transportation safety and research, and some rail programs, was set to expire September 30, 2014. The Highway and Transportation Funding Act of 2014 (P.L. 113-159), enacted on August 8, 2014, extended the authorization of the programs and expenditure authority of the highway trust fund through May 31, 2015. The legislation also transfers $10.765 billion to the highway trust fund (HTF), with $9.765 billion from the general fund and $1 billion from the Leaking Underground Storage Tank (LUST) fund. Nearly all the funding for highways and most of the funding for public transportation is drawn from the HTF. However, the motor fuel taxes that are the main source of HTF revenue no longer raise enough money to support the programs Congress has authorized. Congressional Budget Office projections indicate that the shortfall between revenues and outlays will average roughly $15 billion annually from FY2015 through FY2020. MAP-21 made up most of the difference between motor fuel tax revenue and spending authorization by transferring money from the Treasury general fund to the HTF. As Congress considers surface transportation reauthorization, the funding shortfall is the major issue framing the debate. The alternatives will involve choices among raising motor fuels taxes, cutting spending, finding other revenue sources for the HTF, approving further transfers from the general fund, and seeking to increase private investment in surface transportation infrastructure. MAP-21 made major changes in the program structure for both highways and public transportation. Some of the changes were designed to increase program efficiency by requiring performance measurement and streamlining project development. As these changes are recent, their effectiveness may be difficult to evaluate.