August 19, 2009 -- State Transportation Director Kirk T. Steudle today announced that the Michigan Department of Transportation (MDOT) has once again updated information on the MDOT Web site at www.michigan.gov/highwaybridgereport about the safety of 4,398 state highway bridges.
This is the sixth time MDOT has made bridge safety information available on the Web. State bridge information can be downloaded by route number and/or county, and are current as of July 1, 2009. Only highway bridges greater than 20 feet in length are included; ratings for pedestrian, railroad and locally owned bridges are not included. MDOT is making updates on the Web four times a year.
"We are using limited funding as efficiently as we can," said Steudle, "working year-round to monitor the condition of highway bridges in Michigan. We take highway and bridge safety very seriously and want citizens to be confident that Michigan's bridges are safe, regularly inspected and well maintained."
National Bridge Inspection Standards require MDOT to inspect bridges every two years. The Mackinac, International, and Blue Water bridges are inspected annually, exceeding federal requirements. These three bridges are managed by bridge authorities, and their ratings are not included in the list MDOT has posted to the Web.
Bridge inspectors use a variety of tools to assess bridge safety and structural integrity. The types of inspection performed include bridge safety inspections, fracture critical inspections, fatigue- sensitive inspections and underwater inspections. Non-destructive evaluation and bridge monitoring also is done as needed. Techniques used include calipers to measure the thickness of steel, ultrasonic testing to check for defects in steel, sounding to detect separation of concrete, and monitoring bridge deflections and response to load.
Of the 4,398 bridges on the July 1, 2009 report, 454 bridges are classified with the engineering term of "structurally deficient," meaning they may require rehabilitation or replacement at some time in the future; and 885 bridges are classified as "functionally obsolete," meaning they are outdated and may require modernization at some time in the future. The department is reporting 17 fewer structurally deficient bridges and 34 fewer functionally obsolete bridges in July than it did in April, the fifth time it put bridge inspection information online. Since the April report was released, two new bridges were added to the list and one bridge was removed from the list.
MDOT: Working to improve our state roads and bridges.
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