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National Bridge Inventory Rating Scale
Inspectors rate Michigan's bridges using the National Bridge Inventory (NBI) 0 to 9 rating scale. Inspectors give a rating to each of a bridge's primary elements: deck, superstructure, and substructure.
The Highway Bridge Report shows some bridges built in 2006, 2007 and 2008 as structurally deficient. These bridges are either under construction or the construction has recently been completed and the updated bridge inspection report has not yet been entered into the database.
||VERY GOOD CONDITION - no problems noted
||GOOD CONDITION - some minor problems.
||SATISFACTORY CONDITION - structural elements show minor deterioration
||FAIR CONDITION - all primary structural elements are sound but may have minor corrosion, cracking or chipping. May include minor erosion on bridge piers.
||POOR CONDITION - advanced corrosion, deterioration, cracking or chipping. Also significant erosion of concrete bridge piers.
||SERIOUS CONDITION - corrosion, deterioration, cracking and chipping, or erosion of concrete bridge piers have seriously affected deck, superstructure, or substructure. Local failures are possible.
||CRITICAL CONDITION - advanced deterioration of deck, superstructure, or substructure. May have cracks in steel or concrete, or erosion may have removed substructure support. It may be necessary to close the bridge until corrective action is taken.
||"IMMINENT" FAILURE CONDITION - major deterioration or corrosion in deck, superstructure, or substructure, or obvious vertical or horizontal movement affecting structure stability. Bridge is closed to traffic but corrective action may put back in light service.
|| FAILED CONDITION - out of service - beyond corrective action