The report, "Public Spending on Transportation and Water Infrastructure," updates a similar document published in August 2007. It describes expenditures by the federal government and by state and local governments from 1956, when the Federal-Aid Highway Act authorized construction of the country’s Interstate Highway System, through 2007.

According to the report, spending on highways, mass transit, and aviation dropped markedly from 2003 to 2007 in large part due to the rise in the cost for materials. However, federal spending on infrastructure in 2009 topped $87 billion, $6 billion more than in 2007. That amount included $4 billion in funding from the American Recovery and Reinvestment Act enacted in February 2009.

CBO's analysis found that spending on highways accounted for 43% of expenditures for transportation and water infrastructure in 2007, while transit and aviation accounted for 23%.

While the report acknowledges that spending for carefully selected infrastructure projects can contribute to long-term economic growth -- because it improves infrastructure and raises productivity -- identifying those projects can be a challenge. 

"The federal government could make its current funding more effective by ensuring that the costs of infrastructure projects are allocated across levels of government on the basis of where the benefits are expected to accrue," the report states. "Otherwise, for example, federal funding for infrastructure that provided benefits primarily at the local level could result in too many projects, or projects that are too expensive, being undertaken."

The 62-page report is available at bit.ly/CBO-PSTWI.