April 21, 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 4,397 state highway bridges.
This is the fifth 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 April 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.
"Citizens can be assured that Michigan's bridges are safe, regularly inspected and well maintained," said Steudle. "MDOT and our local agency partners are working year-round to ensure the safest possible travel experience for motorists."
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 is also 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 4,397 bridges on the April 1, 2009 report, 471 bridges are classified with the engineering term of "structurally deficient," meaning they may require rehabilitation or replacement at some time in the future; and 919 bridges are classified as "functionally obsolete," meaning they are outdated and may require modernization at some time in the future. The department is reporting 39 fewer structurally deficient bridges and two fewer functionally obsolete bridges in April than it did last October, the fourth time it put bridge inspection information online. Since the October 2008 report, one bridge has been returned to the county, five new bridges were added to the list, and five other bridges were removed from the list.
MDOT: Working to improve our state roads and bridges.
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