GAO releases information on bridge conditions
Posted December 2, 2015
The Government Accountability Office (GAO) released the 2014 National Bridge Inventory (NBI) data on November 30. Based on the data, GAO has determined that the nation has 610,749 bridges. Of those bridges, 23 percent are on the National Highway System (NHS), and this 23 percent comprise 58 percent of the nation’s total deck area. The deck area of a bridge is the width of the roadway surface of a bridge multiplied by the length of the bridge, which provides an indication as to the size of the bridge.
According to GAO, nearly 25 percent of all bridges are deficient, with 10 percent categorized as structurally deficient and 14 percent categorized as functionally obsolete. Of bridges on the NHS, 4 percent are categorized as structurally deficient while 17 percent are categorized as functionally obsolete. State agencies own about half of all bridges and over 90 percent of NHS bridges.
GAO also identified the following trends:
- Between 2005 and 2014, the nation added over 15,000 bridges and almost 400-million square feet of deck area. Between 2005 and 2012, the number of NHS bridges increased by 2,238. Legislative changes in Moving Ahead for Progress in the 21st Century Act (MAP-21) in 2012 expanded the NHS and reclassified some existing bridges.
- The number of deficient bridges decreased from 2005 to 2014. Specifically, GAO’s analysis of bridge condition data by number of bridges as well as by deck area indicates that structurally deficient bridges decreased by 21 percent between 2005 and 2014, and functionally obsolete bridges decreased by 6 percent; but at the same time, structurally deficient deck area decreased by 20 percent while functionally obsolete deck area increased by 9 percent.
- The number of deficient NHS bridges decreased from 2005 to 2012. Structurally deficient NHS bridges decreased by 20 percent and functionally obsolete NHS bridges decreased by 2 percent. However, functionally obsolete deck area for NHS bridges increased by 6 percent.
- The number of deficient bridges owned by local and state agencies decreased from 2005 to 2014. Among bridges owned by local agencies, the number of structurally deficient bridges decreased by 20 percent while functionally obsolete bridges decreased by 9 percent. Among bridges owned by state agencies, structurally deficient bridges decreased by 24 percent while functionally obsolete bridges decreased by 3 percent. However, functionally obsolete deck area on state-owned bridges increased by 12 percent.
- Improvement of deficient bridges varied by state. Between 2005 and 2014, the number of structurally deficient bridges decreased in 43 states and the District of Columbia (D.C.) but increased in 7 states and Puerto Rico. The number of functionally obsolete bridges decreased in 33 states and D.C. but increased in 17 states and Puerto Rico.
Why GAO did this study
Bridge safety remains a high-priority issue for the nation’s transportation system. Despite recent progress in improving bridge conditions, 10 percent of the nation’s 610,000 bridges were considered structurally deficient as of December 2014, according to the Federal Highway Administration’s (FHWA) NBI.
GAO was asked to determine what available federal bridge data indicate about the condition of bridges throughout the United States. The report examines the current conditions of the nation’s bridges, as well as changes in bridge conditions that have occurred over the last 10 years. GAO reviewed and analyzed FHWA’s NBI data from calendar years 2005 through 2014 — for the nation, each of the 50 states, D.C., and Puerto Rico — by number of bridges and total deck area (which accounts for differences in the size of bridges). GAO also interviewed FHWA officials on bridge conditions.
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