The condition of bridges nationwide has improved markedly since the early 1990s. Of the 590,853 roadway bridges in 2003, the Federal Highway Administration found that 14 percent were structurally deficient and 14 percent were functionally obsolete. About 33 percent of all bridges in 1993 were either structurally deficient or functionally obsolete .
Structurally deficient bridges are those that are restricted to light vehicles, require immediate rehabilitation to remain open, or are closed. Functionally obsolete bridges are those with deck geometry (e.g., lane width), load carrying capacity, clearance, or approach roadway alignment that no longer meet the criteria for the system of which the bridge is a part.1 While the number of structurally deficient bridges steadily declined between 1993 and 2003, the number of functionally obsolete bridges remained constant (figure 2-5).
In general, bridges in rural areas suffer more from structural deficiencies than functional obsolescence (particularly on local roads), whereas the reverse is true for bridges on roads in urban areas (figure 2-6 and figure 2-7). A large number of problem bridges nationwide are those supporting local rural roads: 118,381 of the 160,659 deficient and obsolete bridges in 2003 (74 percent) were rural local bridges. Problems are much less prevalent on other parts of the highway network. Nevertheless, in 2003, 26 percent of rural Interstate bridges and 16 percent of urban Interstate bridges were deficient or obsolete.
1. U.S. Department of Transportation, Federal Highway Administration, Office of Engineering, Bridge Division, National Bridge Inventory database, available at http://www.fhwa.dot.gov/bridge/, as of January 2005.
1 Structurally deficient bridges are counted separately from functionally obsolete bridges even though most structurally deficient bridges are, by definition, functionally obsolete.