However, actual revenues for fiscal year 2008 were about $4 billion lower than the estimates due to fewer purchases of trucks and motor fuel?EUR??,,????'??+two primary sources of account revenue. In the summer of 2008, DOT received indicators that the Highway Account balance was declining faster than expected and developed cash management practices to slow outlays to states but estimated that the account would remain solvent through the end of fiscal year 2008.

Following a large downturn in revenues allocated to the account in August, DOT officials announced on Sept. 5?EUR??,,????'??+three weeks later?EUR??,,????'??+that the practices to slow outlays would begin the following Monday, leaving states little time to adjust. DOT officials recognize that communication with stakeholders could be improved and are developing a plan to improve communication.

Improving mechanisms intended to help maintain Highway Account solvency could reduce the likelihood of a funding shortfall. First, statutory mechanisms designed to make annual adjustments to the Highway Account could be modified and implemented to perform better.

In fact, DOT analyses prepared at GAO?EUR??,,????'???s request show that these modifications could have prevented or at least signaled the fiscal year 2008 decline. Second, DOT could monitor additional indicators throughout the year?EUR??,,????'??+such as changes in vehicle miles traveled?EUR??,,????'??+to help anticipate sudden changes in account revenues. Despite improvements in mechanisms, without either reduced expenditures or increased revenues, or a combination of the two, account shortfalls will likely continue.

DOT officials noted that improved solvency mechanisms would be effective only if the authorization act better aligns expenditures from the account with revenues. In the past, GAO has reported on strategies that could be used to align expenditures and revenues.