How the Government Keeps American Bridges From Collapsing
Our country is rife with structurally deficient bridges—but there's a way to improve them.
America's traffic infrastructure has fallen into a multi-trillion-dollar state of disrepair. The Driveinvestigates how America's crumbling roads, bridges, and tunnels were allowed to decay, and how we can begin fixing them. Last time, we looked at a series of catastrophic bridge failures. In this installment, we look at how authorities go about keeping them from happening.
Most people have at least passing familiarity with aesthetically pleasing spans like the Golden Gate Bridge, in San Francisco, and the Brooklyn Bridge, in New York City. Celebrated in pop art, these beautiful structures have been used to represent the cities they were built to serve. If you've driven across them, the ever-present maintenance crews attest to the amount of work it takes to keep them standing and usable.
What many motorists may not realize is that there are hundreds of thousands of bridges in the United States. Most of them aren't visually impressive structures; many people wouldn't even notice a short, low-walled span as they drove across a tiny creek or gully. But they're as important to road infrastructure as the grand suspension bridges that continue to inspire artists and tourism board directors.
Andrew Herrmann, a past president of the American Society of Civil Engineers, told us that one in nine bridges in the U.S. are classified as structurally deficient, and that, in the nation's 102 largest metropolitan regions, over 200 million trips are taken across deficient bridges every day. Herrmann says that, in general, repair of deficient bridges is trending upward, but it's happening at a sluggish pace. ASCE still recommends spending a lot more money on bridges in order to make them all safe.
"The Federal Highway Administration (FHWA) estimates that to eliminate the nation’s bridge deficient backlog by 2028, we would need to invest $20.5 billion annually," he said. "Only $12.8 billion is being spent currently."
Catastrophic failures aren't common, but that's because state and federal transportation officials take seriously their obligation to protect public safety. Biennial bridge inspections are required by federal law, but when an aging or damaged bridge joins the legion of structurally deficient and functionally obsolete spans, authorities can call for more frequent inspections to ensure that problems don't get out of hand.
"If a bridge is deemed structurally deficient, departments of transportation take various steps, from closing the bridge, to load posting, to speed or vehicle restrictions," Herrmann said. "They can also do emergency repairs and build temporary supports."
So what does "structurally deficient" mean? Officials from the Pennsylvania Department of Transportation, which is responsible for inspecting and maintaining more than 24,000 bridges around the state, explained the federal bridge evaluation standards in an email. Each bridge component—the deck, superstructure, and substructure—is assigned a condition rating, as follows:
9 = Excellent
8 = Very good
7 = Good, some minor problems noted
6 = Satisfactory, structural elements showing minor deterioration
5 = Fair, primary structural elements are sound but showing minor cracks and signs of deterioration
4 = Poor, deterioration of primary structural elements has advanced
3 = Serious, deterioration has seriously affected the primary structural components
2 = Critical, deterioration of primary structural components has advanced and bridge will be closely monitored, or closed, until corrective action can be taken
1 = Imminent failure, major deterioration in critical structural components. Bridge is closed but corrective action may put the bridge back into light service
0= Failed, bridge is out of service and beyond corrective action
N = Not applicable
A condition rating of five to nine means that the bridge is performing as designed, though possibly showing minor signs of deterioration. Bridges in this range are deemed structurally sound, and routine maintenance actions can halt or delay further deterioration. On the other end of the spectrum, a condition rating of four or lower means that deterioration of at least one structural component is advanced, and poor conditions result in the bridge being classified as structurally deficient. Inspectors provide documentation and photographs to structural engineers, who then review the evidence. The engineers, in turn, confirm the assigned condition rating, perform a load rating analysis to determine the bridge's weight capacity, and compare results with those of previous studies to determine if that capacity has changed. They then determine what other actions must be taken.
PennDOT says that, based upon those criteria, it will either make immediate repairs to a structurally deficient bridge, take temporary actions—shoring up weakened sections, restricting traffic from critical areas, or posting weight restrictions, among other options—to keep the bridge open until repairs can be made. In the worst-case scenarios, the agency will close the bridge until repairs can be made.
According to the American Road & Transportation Builders Association's 2016 bridge report, Iowa leads the nation in substandard bridges, with 20.7 percent of its 24,242 spans listed as structurally deficient. Pennsylvania claimed that dubious distinction last year, with 5,050 of its 22,783 bridges on the bad list; this year, that figure is down to 4,783, although that's still almost 21 percent of the state's spans—and the state is still number two in the structurally deficient rankings. (The rankings are not determined solely by the percentage of bridges ranked as structurally deficient.)
PennDOT officials described their process of chipping away at ailing bridges as "a multi-faceted evaluation through maintenance, inspection frequency and load rating, as well as prioritizing the bridge improvement through planning and programming. For a typical bridge crossing a small stream, this process will take around three years."
Clearly, it takes a while for these projects to get from planning to completion. Along the way, funding plays a major role. Funding anything, as anyone who follows politics knows, can be tricky. For its part, PennDOT created a public-private rapid bridge replacement program with the aim of replacing 558 bridges by 2018. On the political front, state lawmakers enacted legislation in 2013, called Act 89, to provide an additional $1 billion in funding for bridge and highway work.
It's clear from the ARTBA report that there's still a lot of work to be done in Pennsylvania and elsewhere. In a report focused upon the most-traveled structurally deficient bridges in America, ARTBA identified 250 spans, almost all of them linking stretches of urban interstate highway and carrying daily traffic volumes from 100,000 to 328,000 trips. Herrmann said that in the Northeast in particular, where heavy traffic combines with climactic extremes and road salt use, bridges take a relentless beating.
Though America's bridges and roads are seeing slow improvement, they're still in rough shape. As Herrmann noted, getting road infrastructure to where it should be, safety-wise, will cost a tremendous amount of money; in the meantime, there are costs associated with the dysfunction and deterioration.
"Currently, 32 percent of America’s major roads are in poor or mediocre condition, costing U.S. motorists $67 billion a year, or $516 per motorist, in additional repairs and operating costs," Herrmann said. "Additionally, 42 percent of America’s major urban highways are congested."
Hermann notes that, due to that congestion, in 2010 Americans wasted 1.9 billion gallons of gasoline, and that, on average, a typical American commuter loses 34 hours—nearly an entire work week—sitting in traffic each year.
Outside major construction projects, Herrmann says there are some relatively simple ways highway authorities can preserve existing bridges and reduce congestion.
"Bridge maintenance at its simplest can be washing road salt and debris off of bridge decks, girders, and piers each spring, and making sure the drainage systems are taking the water away from the structure instead of clogged drains and pipes spilling onto bridge components," he said. (Remember the Mianus River bridge collapse in Connecticut? Inspectors surmised that clogged drains may have caused critical bridge components to fail more quickly than they would have otherwise.)
Staying on top of repairs to protective coatings, like paint and waterproofing, and potholes is also important, as moisture and road salt can seep into cracks in paint and concrete and damage structural components. Once corrosion begins, the damage is compounded. As steel parts corrode, they can expand up to seven times their original volume, which can further damage concrete and cause still more potholes.
The good news is that state and federal highway agencies work together and share data in order to provide the most up-to-date information on highway maintenance and construction practices. For example, failures like Minneapolis's I-35W bridge collapse, in 2007, and the Hoan bridge fracture in Wisconsin, in 2000, have been cause for PennDOT to institute many changes, both in policy and practice.
If you haven't looked into the conditions of roads and bridges where you live, now is the time. The fastest way to get big projects done is by pressuring elected officials to fund them. You, John and Jane Q. Taxpayer, are the one who can apply such pressure.
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