M-66 over Middle Branch River

Osceola County, Michigan · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

• M-66 over Middle Branch River in Osceola County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
• It was built in 1939, making it 86 years old at the 2025 inventory.
• It carries about 1,485 vehicles a day (traffic count year 2007).
• Its listed owner is the state highway agency.
• It is one of 60 of the 103 inventoried bridges in Osceola County rated fair (58.3%); 7 (6.8%) are rated poor.
• Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
• Its condition class and component ratings are unchanged from the 2024 inventory.
• Its most recent inspection on record is dated September 2024, on a 24-month routine inspection cycle.
• It is coded scour critical (NBI item 113 = 3): scour critical: foundations unstable for the assessed or calculated scour.
• A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

View this bridge on a map → (44.11106, -85.14752)

Component ratings

Bridge details

Source: FHWA National Bridge Inventory, 2025 data as reported by the Michigan department of transportation.

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Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.