The U.S. Chamber of Commerce released what it says is a first-of-it-kind annual index designed to look over time at how U.S. transportation infrastructure is serving the needs of the U.S. economy and business community.

The new "Transportation Performance Indexes" show a significant decline over the last five years in how America's transportation infrastructure is serving the needs of domestic commerce, international trade, and the overall U.S. economy.

The annual Transportation Performance Index combines indicators of supply (availability), quality of service (reliability, predictability, safety) and utilization (potential for future growth) across all modes of passenger and freight transportation - highway, public transportation, freight railroad, aviation, marine and intermodal - to show how well the U.S. transportation system is serving the needs of businesses and the overall U.S. economy.

The national index is 51.24 in 2008, which is a slight improvement from 50.74 in 2007. However, the moving average, which smoothes the annual variations, reveals a clear downward trend from 2003 to 2008, demonstrating that the performance of the U.S. transportation system is not keeping pace with the demands on that system.

This week's release covers the time period from 1990 to 2008, the last year for which national-level date is available. Over this period the index - or the performance of our transportation system - increased only about 6 percent, while U.S. population during that time period grew 22 percent, passenger travel grew 39 percent, and freight traffic grew 27 percent.

"The performance of the nation's transportation system is not keeping pace with the rate of growth of the demands on that system," said Thomas J. Donohue, president and CEO of the U.S. Chamber of Commerce.

"As our economy recovers, the nation's transportation infrastructure must be prepared to meet the projected growth in freight and population. In fact, a 10-point improvement in the new national transportation index could generate 3 percent more growth in the nation's Gross Domestic Product. However, our index shows that from now through 2015 there will be a rapid decline in the performance of the system if we continue business as usual. Right now we're on an unsustainable path."

"The bottom line is this: our nation's deteriorating infrastructure is placing a major drag on our economic growth," said Donohue. "We must focus on improving the way transportation delivers for business, removing barriers to maintaining, modernizing and expanding our nation's transportation infrastructure, and driving increased public and private investment."