February 2008 – AggBeat
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by Tina Grady Barbaccia, Senior Editor
Deficient Bridge Inventory Shows Only Slight Improvement
The I-35 bridge collapse in Minnesota focused the nation’s attention on deteriorating bridges, but highway engineers have long been working to reduce the percentage of structurally deficient and functionally obsolete bridges. A new study reveals that despite increased efforts, little progress has been made over the past year. An exclusive survey conducted by Better Roads magazine and sponsored by CONTECH Bridge Solutions Inc., shows that across the nation the percentage of structurally deficient and functionally obsolete bridges improved by just 4 percent during the past year to 24.1 percent. The findings, based on a survey among highway professionals within all 50 state departments of transportation and the District of Columbia, represent the most current data available on bridge conditions.
“The gain is very slight,” warns Ruth Stidger, editor-in-chief of Better Roads, a sister publication to Aggregates Manager. “Our 2007 survey counts 1,682 fewer structurally deficient or functionally obsolete bridges than in 2006, which means that only 1 percent of the 145,996 bridges classified as substandard a year ago, were improved.”
Since 2004, more than 6,700 bridges have been taken off the substandard count, but even that small progress has come at a price. “Bridge repair and replacement is enormously expensive,” Stidger notes, “and as agencies have spent more of their money on bridges, they have had less to invest in pavement quality and highway capacity improvements.”
Funding represents the greatest challenge for agencies. Just 41 percent of responding agencies feel they will be able to lower the percentage of deficient bridges next year. “The spike in construction materials and diesel fuel has eroded the spending power of our state and local road agencies, and the pace of bridge improvements seems to be slowing,” Stidger adds.
The study provides further insight into the decaying bridge inventory by breaking out structurally deficient bridges from those that are functionally obsolete. Structurally deficient bridges are considered more serious, since they have structural problems that require limiting weight or more frequent inspections. Some must be closed. About 54 percent of the substandard bridges fall into this category, compared to 46 percent, which are functionally obsolete. Functionally obsolete bridges may be in good condition, but don’t meet the needs of current traffic. Responding agencies use a standard sufficiency rating system, developed by the Federal Highway Administration, to rate each bridge. Federal law mandates that all bridges must be inspected every two years.
States with the highest percentage of structurally deficient/functionally obsolete bridges include Rhode Island (53 percent); Hawaii (40 percent); New York (38 percent); West Virginia (37 percent); Massachusetts, Vermont (36 percent); Connecticut (33 percent); Missouri, North Carolina (31 percent); and Louisiana, Maine, New Hampshire (30 percent).