California in recent decades has spent billions retrofitting its bridges for earthquakes, but in the wake of Thursday's bridge collapse in Washington state, critics say the Golden State is still lagging behind most other states in the quality of its bridges.
Thousands of bridges in California are classified as "structurally deficient" by federal transportation authorities, meaning they have some kind of defect that needs regular inspection. Thousands more were built so long ago that they -- like the bridge that collapsed Thursday after its trusses were hit by a big rig -- are considered "functionally obsolete," meaning they were designed years earlier when truck loads and traffic were much lighter.
"California went in early and big on highway building and the highway-oriented lifestyle," said David Goldberg, spokesman for Transportation For America, a coalition of groups dedicated to improving the nation's infrastructure. "So California has far and away the largest number of structurally deficient bridges that are needing repair or replacement."
State transportation officials say that almost all of the state's bridges have been strengthened by two decades of seismic upgrades that followed the Loma Prieta and Northridge earthquakes in 1989 and 1994. They say state-owned bridges are inspected every two years and closely observed by maintenance crews in between.
"If our inspectors find any kind of problem, it's immediately addressed," said Caltrans spokesman Bob Haus. "We go into action right away. We are not going to have bridges open if there is any danger to the public."
But that doesn't mean every California bridge is in good shape.
The American Society of Civil Engineers gave California a "C-minus" grade for its transportation infrastructure -- from bridges to roads and dams -- in last year's report card. It said that 4,178 of the 24,812 bridges, or 16.8 percent, in California are "functionally obsolete."
Transportation for America in 2010 ranked California the 18th worst state in terms of the percentage of structurally deficient bridges, which by federal law must be inspected every year.
The group found:
In Washington state Thursday, a trucker was hauling a load of drilling equipment when it bumped against the steel framework over an Interstate 5 bridge. He looked in his rearview mirror and watched in horror as the span collapsed into the water behind him. Two vehicles fell into the icy Skagit River.
Amazingly, nobody was killed. The three people who fell into the water escaped with only minor injuries.
California has 211 "through truss" bridges like the span that collapsed in Washington, although only 84 have limited clearances above the roadway. Of those, 16 are in the Bay Area, including the eastern span of the Bay Bridge and the Carquinez and Richmond-San Rafael bridges.
Defined as a bridge in which the supporting framework is alongside or over the roadway, truss spans with restricted room between the tops of trucks and the bridge's superstructure can pose a hazard.
Caltrans on Friday inspected 26 state-owned through-truss bridges, remeasured the posted clearances and verified the signage, said agency spokesman Will Shuck. The state posts large signs on bridges with less than 15½ feet of clearance; a standard big rig truck is 14½ feet.
"We have also started reaching out to cities and counties with these types of bridges to alert them of the situation," Shuck said.
Barry LePatner, a lawyer and founder of Save Our Bridges, said that the older bridges were simply not designed for today's "18 wheelers or overloaded trucks."
The bridge in Washington that collapsed was not rated structurally deficient and had a grade of 57.4 under a federal rating system. Anything below 50 would be considered especially worrisome, said Hassan Astaneh, professor of engineering and bridge engineering at UC Berkeley.
More significant, he said, was the fact that the bridge was "fracture critical," an engineering term that means that damage to one structural component can cause the entire structure to collapse. The bridge that collapsed in Minneapolis in 2007 was also fracture critical, he said.
Caltrans put out a request for proposals in April 2011 for inspection services for fracture critical bridges. It listed 48 bridges for inspection. California has 1,038 fracture critical bridges, according to Caltrans spokesman Shuck.
The Associated Press contributed to this report.