From major spans over the Mississippi River to overpasses on traffic-choked arteries skirting Chicago, some 200 bridges throughout Illinois are in need of replacement or repair because of their outdated, insufficient design and their advanced deterioration.
That particular combination of red flags has emerged as a vexing problem around the country, as bridges are pushed beyond their expected lifespans and assaulted by ever-increasing traffic loads.
In Illinois, with too little money to throw at the problem, state transportation officials have gone into triage mode, prioritizing the busiest bridges in the worst shape for overhaul, implementing weight limits or closure orders on others, and closely monitoring the rest.
"For a bridge to fall into both of those categories it is — how should I put it? — it should be a wakeup call," said Keith Brandau, a Champaign-based structural engineer for the firm Fehr Graham who has helped inspect bridges for local governments in Illinois.
An Associated Press review of national bridge records found that some 7,795 bridges nationwide are classed as both "fracture critical" and "structurally deficient," a combination that experts say is especially problematic.
The first designation refers to bridges that were designed with no redundant protections, putting them at risk of collapse if a single, vital component fails. The "structurally deficient" label is attached to bridges that need rehabilitation or replacement because at least one major component has advanced deterioration or other problems that have led inspectors to deem its condition "poor" or worse.
The most recent federal data available identifies 189 such bridges scattered around Illinois. Pinning down an up-to-date figure is difficult, because the numbers fluctuate as bridge improvements and repairs are made to some structures while others deteriorate and slip into disrepair.
"We don't feel that the public should be worried," said Carl Puzey, chief of Illinois' Bureau of Bridges and Structures, which subjects fracture critical bridges to a more intensive inspections regime than the rest of the state's roughly 26,000 bridges.
"In very rare cases, if it's necessary to ensure the safety of the traveling public, we will close the bridge. So, if a bridge is open, it's safe," he said.
Until recently, Peoria had four crossings in both categories — all of them over the Illinois River — including both directions of Interstate 474. That span, which carries nearly 15,000 cars and trucks a day, underwent deck repairs in 2011 and is no longer deemed "structurally deficient."
The other two in the Peoria area are the U.S. 24 bridge and the Cedar Street bridge, a cantilevered deck truss built in 1932 that has had some interim work done to shore up its steel over the last decade.
Mayor Jim Ardis says the city government is aware of the problems, but is also accustomed to feeling like "we're the last ones to get anything" when it comes to the federal and state funding needed to make repairs.
"It is not surprising that these things keep getting pushed down the road," he said. "With the fiscal state of our state ... we're really pushing the envelope on potential liabilities in all of these bridges."
Illinois' at-risk bridges also include the span over the Des Plaines River south of Joliet along Interstate 80, one of the most important transcontinental routes between New York and San Francisco. The west-bound and east-bound bridges were built in 1965 and now carry an average of 37,000 cars and trucks each day.
Others falling in both categories include the Quincy Memorial Bridge over the Mississippi River in western Illinois and some in the far southern corner of the state in Cairo. Many cross rural creeks and streams.
Three ramps leading to the busy Poplar Street Bridge, which soars past St. Louis' Gateway Arch, are in both categories. Also on the list is an elevated section of the Kennedy Expressway across Chicago's Ashland Avenue that carries 300,000 vehicles a day. Extensive repairs are under way.
The main problem in battling the maintenance backlog is money. It takes hundreds of millions of dollars — sometimes as much as $1 billion — to replace a major crossing with a heavy traffic load.
Federal fuel taxes, a main source of highway funds, do not keep pace with inflation and have not been raised since 1993. Meanwhile, politicians in control of scarce funds are often more keen to take credit for brand new facilities than to support something as un-sexy as bridge maintenance.
"Costs are up, gas tax revenues are down, and our decision makers do not have the backbone to tell us so and act on this," said Joseph Schofer, a professor of civil engineering and transportation at Northwestern University.