Friday, November 13, 2009

Shockingly high number of US bridges remain sub-standard

Better Roads has a looong, data-rich study of bridges and roads in the US. Behold the fruits of decades of underinvestment!: The Better Roads Bridge Inventory is an exclusive, award-winning annual survey that has been conducted since 1979. Bridge engineers from every state and Washington, D.C., are set a survey with both qualitative and quantitative questions. The Federal Highway Administration, in consultation with the states, has assigned a sufficiency rating, or SR, to each bridge (20 feet or more) that is inventoried. Formula SR rating factors are as outlined in the current Recording and Coding Guide for Structures Inventory and Appraisal SI&A of the Nation’s Bridges. The qualitative data is gathered through a questionnaire about major issues concerning bridge conditions and maintenance.

There are 597,787 bridges in America, 288,920 interstate and state bridges and 308,867 city/county/township bridges. But 21.6 percent – or 62,504 – of the interstate and state bridges are structurally deficient (SD) or functionally obsolete (FO). And 25.7 percent of the city/county/township bridges – or 79,394 – are SD/FO.

Maintenance, personnel, training, age, environmental restrictions, a need to minimize traffic disruption, capacity and corrosion issues remain major barriers to lowering the rate of bridges becoming deficient, despite some respite coming from stimulus fund money.

…Regardless of what the official statistics show about the number of bridges that are SD and FO, some bridge engineers say that we should look at the square footage of SD and FO bridges to get a true picture of the situation. Ray Mumphrey, highway bridge program manager with the Louisiana Department of Transportation, says that while the number of SD/FO bridges may have decreased, the square footage may actually be increasing. “It may look like we’re making progress [in the nation] with the number of deficient bridges, however larger bridges are becoming deficient which increases the square footage of deficient bridges,” Mumphrey says. “There are a lot of interstate [bridges] becoming deficient, although the numbers of deficient structures may have gone down.”…

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