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Analysis Reveals 58,495 U.S. Bridges Are Structurally Deficient

By Catherine A. Cardno, Ph.D.

The American Road & Transportation Builders Association has analyzed the raw 2015 bridge inspection data that was recently released by the Federal Highway Administration, and determined that 9.6 percent of the nation's bridges are structurally deficient.

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The Arlington Memorial Bridge, in Washington, D.C., is one of 58,495 bridges deemed structurally deficient in the United States in 2015. This represents 9.6 percent of the nation’s bridges, a slight decrease from recent years. © Benoît Prieur/Wikimedia Commons/CC-BY-SA-4.0

March 15, 2016—Each year, the Federal Highway Administration (FHWA) releases raw data gathered over the course of 12 months as part of its National Bridge Inventory Database. Using the 2015 raw data released earlier this year, last month the American Road & Transportation Builders Association (ARTBA) released a state-by-state breakdown of the number of structurally deficient bridges in the United States. In all, 58,495 bridges out of the 609,539 bridges in the United States are currently rated as structurally deficient. This equates to 9.6 percent of the bridge stock in the nation.

The FHWA oversees the National Bridge Inspection program, which calls for regular assessments of all public vehicular bridges more than 20 ft in length—regardless of ownership or funding—in an effort to ensure that they remain safe. The FHWA also maintains the National Bridge Inspection Standards (NBIS), the federal regulations governing bridge inspections that states and federal bridge-owning agencies are required to follow. 

"Safety is the number one priority at the U.S. Department of Transportation [DOT], and that includes keeping our nation's bridges safe," said Joseph L. Hartmann, Ph.D., P.E., the director of the office of bridges and structures at the FHWA, which is an agency within the U.S. DOT. Hartmann wrote in response to written questions posed by Civil Engineering online. 

The bridge inspection program involves thousands of certified inspectors who work with the FHWA's division offices, state transportation departments, and federal agencies to evaluate the condition and safety of bridges in the United States, according to Hartmann. Under the program, a bridge is rated between 0 and 9. A bridged rated 9 is in "excellent" condition, while any crossing rated 4 or lower is classified as structurally deficient.

"Bridges are inspected on a routine basis, typically every 24 months, and the results are reported to the FHWA," Hartmann explained. "Under the inspection program, defects with bridges are detected early on, so they can be addressed in a timely manner or a load posting can be implemented," he said. Such postings limit the weight of vehicles that are allowed on a bridge until structural deficiencies are addressed. "If a bridge is identified with a defect severe enough, the bridge is closed," he added.

In analyzing the 2015 data, ARTBA determined that the state with the greatest number of structurally deficient bridges is Iowa, with 5,025, representing 20.7 percent of its bridge stock. The state with the second-highest number of structurally deficient bridges is Pennsylvania, with 4,783 deficient bridges, or roughly 21 percent of its bridge stock.

Focusing on the percentage of a state's bridges that are structurally deficient only changes the rankings slightly: Iowa and Pennsylvania are ranked 3 and 2 respectively; Rhode Island has the highest percentage, 23.2, which equates to 178 bridges.

The best-performing state numerically is actually a district: the District of Columbia has only 10 structurally deficient bridges, or just 3.9 percent of its bridge stock. (Although one of those, the Arlington Memorial Bridge, made headlines last year when some lanes were removed from service and weight restrictions were placed on the bridge, and earlier this year when the National Park Service, the bridge's operator, announced that the entire bridge may need to be closed entirely to all but foot traffic within five years if significant improvements are not made by then.) 

Nevada ranked second-best numerically with only 35 structurally deficient bridges, or 1.8 percent of its bridge stock. When the percentages are looked at, Nevada ranks first and Texas comes in a close second, with just 1.9 percent of its bridge stock—1,008 bridges—ranking as structurally deficient. (The District of Columbia is the sixth best performer by percentage.)

Combined, these structurally deficient bridges see a total of 204 million daily crossings, according to ARTBA. The highest number of daily crossings seen by a structurally deficient bridge is the Interstate 5 Bridge over El Toro Road in Orange County, California, which sees 328,000 crossings daily. The bridge was originally built in 1969 and was rated structurally deficient this year after passing its inspection in the previous two years.

ARTBA did find some positive news in its analysis. Between 2014 and 2015, the number of structurally deficient bridges overall in the United States decreased by 2,574, and by 8,254 since 2012. In its 2013 Report Card for America's Infrastructure, ASCE cited the 2012 ratings in giving the nation a grade of C+ for the state of its bridge infrastructure. (The Society's next report card will be issued in 2017.)

"Things definitely are improving, and they continue to improve every year," says Alison Premo Black, Ph.D., the chief economist for ARTBA, who conducted the analysis for the report. "We track bridge investment very closely [and] we know that state and local governments are really trying to address these issues," she explains. "They've invested a lot of funds in bridges over the last 10 to 15 years, and over that time we have seen some incremental progress both in reducing the number of deficient bridges as well as the percent of our inventory that is classified as structurally deficient.

"The challenge, though, is that the pace of that improvement is very slow," she notes. While the overall inventory of structurally deficient bridges might be decreasing by 2,000 to 2,500 bridges annually, at that pace it will take more than 20 years to eliminate just the existing inventory, Black points out. "We're just talking about minimal amounts at the margin, to simply maintain what we have and try and stem the deterioration of the system," she says.

Federal funds, on average, provide 52 percent of a state's annual department of transportation capital outlays for state highway and bridge projects, according to ARTBA. However, this amount varies widely between states. For example, Rhode Island, the state with the highest percentage of structurally deficient bridges, receives more than 80 percent of its annual state department of transportation outlays from the federal government, while Iowa and Pennsylvania respectively obtain 59 percent and 45 percent of their funding from federal sources. The best-performing states and district—Nevada, Texas, and Washington, D.C.—respectively receive 52 percent, 41 percent, and 52 percent of their state and district DOT funding for highway and bridge capital outlays from federal sources. 

Although the federal funding for state projects is already extremely high in some states, "[ARTBA's] position is to advocate for increased investment from all levels of government, but in particular the Federal Aid Highway Program," Black says. Increased funding will help across the board.

"Sometimes you can't always see that there are some structural challenges on a bridge that need to be fixed," Black notes. "This is a real issue that affects every community in America, and that affects everybody driving over these bridges," she says. "To really address these issues we need to be investing in our system.

"All levels of government need to examine what needs to be invested, to truly make the improvements to the system," Black says. "And to not only just maintain our system, but to make the improvements that are really going to help motorists and commuters, and businesses with their location decisions—all of those things that tie into our economy."

Black also points to the importance of successful, bipartisan, state-level initiatives to increase funding to improve the quality of transportation infrastructure. "We've had 16 states raise their gas taxes over the last three years," she notes. "We have tracked over 750 state and local bond initiatives over the last 15 years [and] 72 percent of those were approved by local voters—so we know that people are willing to pay for transportation and investment." 

What it boils down to, she says, is "having the political will to actually make that happen."

The full ARTBA analysis of the structurally deficient bridge data is available on its website. The raw 2015 National Bridge Inventory ASCII files can be downloaded from the FHWA's website.



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