The National Bridge Inventory data documents the conditions of bridges on all public roads, regardless of their ownership. Bridges are evaluated and rated as “not deficient,” “functionally obsolete,” or “structurally deficient.” A bridge rated “functionally obsolete” or “structurally deficient” is not necessarily unsafe for all vehicles. Rather, it typically has an older design that lacks modern safety features such as adequate shoulder space, an appropriate railing system, or other features. Strict observance of signs limiting traffic or speed on the bridge will provide adequate safeguards for those who use bridges rated as structurally deficient or functionally obsolete.
As indicted in the above figure, the number of structurally deficient bridges has been declining since 1992. The number of functionally obsolete bridges has stayed relatively constant since 1992. Of the 603,254 bridges in the United States as of December 2009, 71,179 were rated structurally deficient and 78,468 were rated functionally obsolete.
Data Source: US Department of Transportation, Federal Highway Administration, Office of Bridge Technology, National Bridge Inventory
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