AASHTO Journal, 4 December 2015
A new report by the U.S. Government Accountability Office finds that while states have been reducing the number of problem bridges on the roadway network, one in four bridges is deficient in some way.
“Nearly 25 percent of all bridges are deficient,” the GAO said, “with 10 percent categorized as structurally deficient and 14 percent categorized as functionally obsolete.”
Those rated structurally deficient have one or more structural elements, such as bridge deck, in poor condition. Functionally obsolete structures have a configuration or design that may no longer be adequate for the traffic it serves, the agency said, such as being too narrow or having inadequate overhead clearance.
That does not mean the structures are no longer safe for traffic. Authorities close bridges when they are judged as no longer safe to use. However, bridges rated deficient may be posted for weight limits and may need additional maintenance or repairs to improve their condition.
The GAO conducted its audit and reported on bridge conditions in response to a request by leaders of the House Transportation and Infrastructure Committee, while that panel was putting together its draft of a long-term surface transportation bill.
The GAO said it briefed committee staff Sept. 22 about its preliminary findings, published a final report Oct. 29 and publicly released it Nov. 30.
The agency limited its analysis to structures classified as highway bridges in the Federal Highway Administration’s National Bridge Inventory that are at least 20 feet in length, which are those subject to National Bridge Inspection Standards.
Based on 2014 NBI data, the GAO counted 610,749 bridges across the country. Of those, 23 percent are on the National Highway System and account for 58 percent of the nation’s total bridge deck area. State agencies own about half of all bridges and over 90 percent of NHS bridges, it noted.
A summary of the final House-Senate transportation bill said the measure “expands funding available for bridges off the National Highway System.”
Of NHS bridges, it said 4 percent are structurally deficient while 17 percent are categorized as functionally obsolete.
It also said that between 2005 and 2014, the nation added over 15,000 bridges and almost 400 million square feet of deck area.
Meanwhile, the number of deficient bridges decreased from 2005 to 2014 as state departments of transportation, local agencies and the federal government invested more in infrastructure improvements, partly through the recovery program Congress passed in response to the 2008 financial crises.
GAO’s analysis found the number of structurally deficient bridges decreased 21 percent in that 2005-2014 period, and obsolete bridges decreased by 6 percent. In addition, structurally deficient deck area shrank by 20 percent but functionally obsolete deck area grew by 9 percent.
State and local agencies reduced the number of deficient bridges they owned by 20 percent while obsolete bridges decreased by 9 percent. However, functionally obsolete deck area on state-owned bridges increased by 12 percent.
The improvements varied by state. Between 2005 and 2014, the number of structurally deficient bridges fell in 43 states and the District of Columbia but increased in seven states and Puerto Rico. The number of obsolete bridges shrank in 33 states and D.C. but increased in 17 states and Puerto Rico.
