Traffic came to a screeching halt one Thursday in May 2013 when a truck carrying an oversize load hit Washington's 1-5 Skagit River Bridge, causing a partial collapse of the 58-year-old steel truss bridge and sending three vehicles into the water below.
While there were no casualties and repairs are under way, the incident has drawn attention to the condition of aging bridges across the nation. And now that road-trip season is in full swing, we wanted to take a closer look.
Consider Boston's Storrow Drive, a double-deck roadway abutting Back Bay. Although nearly 60,000 cars cross this bridge heading west daily, few drivers may realize the condition of what's beneath their tires: the structure, which carries the road's westbound lanes over the eastbound, has been deemed "entirely insufficient" based on an evaluation formula used by government bridge inspectors.
The Storrow bridge's design flaws and corroding support beams make it one of many highly trafficked bridges in the nation to earn a low sufficiency rating--a score that indicates a bridge's sufficiency to stay in service. While a bad rating doesn't necessarily mean danger is imminent, when combined with high traffic volumes, it signals possible trouble for a bridge.
A majority of the nation's dangerous bridges are found in the Northeast, including No. 2 Pulaski Skyway in New Jersey. The disparity can be partly blamed on local conditions, according to Brian Leshko, a bridge expert with HDR, a global engineering firm based in Omaha, NE: steel tends to corrode more quickly in humid climates, especially where salt is used to de-ice roads in the wintertime.
One thing these bridges have in common, whether in Oregon or Louisiana, is age. All are more than 45 years old, and they've got company nationwide. Many structures from the bridge-building boom of the 1950s were designed for a 50-year lifespan, Leshko says. "When you do the math, you can see why we are where we are."
Although many insufficient bridges are undergoing major rehabilitation or replacement, such improvements require years of work, and in the meantime millions of cars still rely on them daily. William Ibbs, professor of civil engineering at UC Berkeley, points out that the risk is often a fiscal one: these troubled bridges are expensive to fix, yet left untended, they could be forced to close, costing the people and industries that use them time, money, and inconvenience.
As the nation's infrastructure continues to age, more large-scale projects will be necessary to keep our bridges in safe working order, according to David Goldberg of advocacy group Transportation for America, which recently released a report claiming 1 in 9 bridges is deficient, affecting more than 260 million Americans daily.
"We're going to see a wave of bridges that are going to need major overhaul or replacement," Goldberg says. "That's something we need to be ready for."
Read on to find out if your travel plans cross any of America's most troubled bridges. --Sarah L. Stewart
We analyzed 2012 data from the Federal Highway Administration for nearly 700,000 bridges, focusing on the subset with an average daily traffic volume (ADT) of more than 50,000 vehicles. We ranked those bridges according to their sufficiency rating (SR): a percentage from 0 (worst) to 100 (best), which is determined by a government formula that factors in a bridge's structural adequacy, safety, serviceability for modern use, and essentiality to the public. As civil engineer William Ibbs put it, "Those two variables are the standard measures we use for assessing bridge risk." The resulting list reveals America's high-traffic bridges with the worst sufficiency ratings (after removing 11 that are closed or have substantial improvements either completed or expected to be completed in the next year).
See More of America's Most Dangerous Bridges ADT: 57,770 SR: 0% This double-deck roadway abutting Back Bay has been a headache practically since it opened in 1951. The problem: the pavement of the upper deck is too thick, straining the corroding steel beams that support the structure from underneath. Numerous rounds of costly interim repairs (most recently in 2012–13) have kept the artery open, but they’re merely stopgaps to extend its life through 2018 while longer-term solutions are weighed. Photo: Kim Karpeles / Alamy
See More of America's Most Dangerous Bridges ADT: 61,500 SR: 2% Herbert Hoover was president when this 3 ½-mile-long steel structure was completed, at which time its estimated traffic volume was 5,500 vehicles per day. Eighty years later, its capacity demands have increased more than tenfold, and its structural steel and concrete are rusting. A $1 billion rehabilitation under way now through 2016 should address these and other concerns throughout the length of the Skyway, including this 550-foot section that crosses 135 feet above the Passaic River. Photo: dbimages / Alamy
See More of America's Most Dangerous Bridges ADT: 61,500 SR: 2% The Skyway’s other 550-foot river crossing will also benefit from the $1 billion rehab, which includes a deck replacement, repairs to its concrete and steel supports, and an enhanced ability to handle seismic events. The repairs will close the Skyway to northbound traffic for 24 months starting in 2014, but southbound traffic will remain on the bridge during construction. Photo: Tony Kurdzuk/Star Ledger/Corbis
See More of America's Most Dangerous Bridges ADT: 142,600 SR: 3% Opened in 1940, this Brooklyn span is the only drawbridge on New York’s Belt Parkway. Its outdated design has led to frustrations, including a major traffic jam caused in July 2012 when the bridge became stuck in the up position for more than an hour. Construction is just beginning on a new, 60-foot-tall fixed bridge to replace the Mill Basin Bridge; cars will continue to use the old structure until the new one is complete in 2017. Photo: Mario Burger/ Burger International Photography
See More of America's Most Dangerous Bridges ADT: 73,000 SR: 5.3% In a May 2011 inspection, this 1940 concrete bridge scored the lowest possible rating for its structural evaluation—an appraisal of its overall condition—that is permitted for a bridge that remains open to traffic. The Federal Highway Administration defines a structural evaluation score of 2 as “requiring high priority of replacement,” as compared to a bridge built to current standards. Photo: Google
See More of America's Most Dangerous Bridges ADT: 97,870 SR: 9% At nearly 1½ miles long, this span across the 200-foot depths of Lake Washington is the longest floating bridge in the world. But time has taken a toll on the 50-year-old engineering marvel: crews have repaired 30,000 feet of cracks in its concrete pontoons, and its design makes it susceptible to closure during windstorms. A wider, stronger replacement—which will be the world’s new longest floating bridge when it opens in 2015—is currently under construction. Photo: WorldFoto / Alamy
See More of America's Most Dangerous Bridges ADT: 63,000 SR: 9.9% While the arching profile of this cantilever bridge may be aesthetically pleasing, its steep grades have been cited as a traffic concern, especially given the high volume of trucks the bridge carries along this major east-west corridor. Proposals to replace the 60-year-old structure have been discussed for more than a decade, but so far improvements have been limited to repairs and maintenance, including a $5.7 million project in 2012 to remove rust and replace damaged rivets. Photo: David Backlin
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