NASHVILLE, Tenn. -- The Tennessee Department of Transportation's commissioner on Monday outlined the status and safety of Tennessee's 19,519 bridges.

Related: Tennessee Bridge Facts (pdf)

As of January 31, 2008, only 2.4 percent of interstate bridges in Tennessee are deficient, while 4.7 percent of all state-owned bridges are classified as structurally deficient, according to the state.

That is the sixth lowest percentage of structurally deficient bridges in the nation, according to the data from the Federal Highway Administration.

"Tennessee is fortunate to have one of the best transportation systems in the nation, including a first-rate bridge program," said Nicely in a press release. "We have invested more than $1.7 billion in bridges in the last two decades and will continue that commitment into the future."

TDOT said they dedicated more than $130 million to the replacement and repair of Tennessee's bridges in fiscal year 2007/2008 and will dedicate another $116.6 million for bridge repair and replacement in fiscal year 2008/2009.

The state said they are currently implementing additional training for bridge evaluators, an updated load permitting process to enhance the department's ability to issue permits, and is contracting with the U.S. Geological Survey to utilize sonar scan technologies to enhance underwater bridge inspections for some bridges, according to a press release.

A report issued on Tuesday by the American Association of State Highway and transportation officials touted the safety of U.S. bridges, but concluded that one out of every four needs to be modernized or repaired.

The report outlines the challenges and key findings:

Age - Usually built to last 50 years, the average bridge age in this country today is 43, with one in five bridges over 50 years old. As age and traffic increase, so does the need for repair.

The Price Tag - Based upon data from the Federal Highway Administration, the cost to repair or modernize the country's bridges is $140 billion, assuming all the bridges were fixed immediately.

Traffic Congestion - Many of the nation's large-scale bridges have become chokepoints on the country's freeway system, and a drain on the nation's economy. The top 10 highway interchange bottlenecks cause an average of 1.5 million truck hours of delay each year.

Soaring Construction Costs - The costs of steel, asphalt, concrete and earthwork have risen by at least 50 percent in the past five years, forcing delays of bridge improvements and replacements. Nearly every state faces funding shortages that prevent them from the kind of on-going preventive maintenance, repair and replacement needed to keep their bridges sound indefinitely.

Aug. 1, 2008 marks the one-year anniversary of the Interstate 35W bridge collapse in Minneapolis , which killed 13 and injured more than 100.

Related Links:

Report Says 1 In 4 Bridges Needs Upgrading

Tennessee Bridge Information

Federal Highway Administration