How Safe Are Your State's Bridges?

Aug. 2, 2007 — -- Numbers can never match the horror of Wednesday's Minnesota highway collapse, but the statistics on deficient bridges are staggering.

Thirteen percent of bridges in the United States share the same "structurally deficient" rating as the bridge that collapsed in Minneapolis, including 30 percent of bridges in Oklahoma, 26 percent in Rhode Island, and 25 percent in Pennsylvania. It could not immediately be determined how many bridges are currently closed across the country as unsafe, and the U.S. Department of Transportation didn't return calls seeking comment today.

Minnesota's bridges are actually some of the country's safest: Only 12.2 percent of the state's bridges are rated "structurally deficient" or "functionally obsolete," ranking it third best behind Arizona (10 percent) and Nevada (12 percent), according to 2006 data from the Bureau of Transportation Statistics.

Only 8.8 percent of Minnesota's bridges are, like the collapsed I-35W span, rated "structurally deficient," the 14th lowest total in the country.

Overall the data indicates that 26.2 percent of the nation's bridges are in need of repair or do not meet the highest safety standards. Bridges in this category are rated either structurally deficient or functionally obsolete, according to the statistics.

Washington, D.C., has the country's least safe bridges, with 63 percent of the district's 245 bridges rated either structurally deficient or functionally obsolete.

A bridge is rated "structurally deficient" if it's in poor condition and is deemed ill-equipped to handle the demands of the traffic load it carries, according to Susan Lane, manager of codes and standards with the American Society of Civil Engineers, which evaluates bridge safety.

Structurally deficient bridges don't need to be closed, though they usually do require some repairs or weight restrictions, said Steve Chizmar, a spokesman for the Pennsylvania Department of Transportation.

A span is "functionally obsolete" if it fails to meet certain traffic standards, Lane said. For example, the bridge may be too narrow to hold both traffic lanes and shoulders, or it may hang too low, leaving inadequate clearance for trucks and trailers on a roadway below.