Royston over Big Thornapple Drain

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

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

• Royston over Big Thornapple Drain in Eaton County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
• It was built in 1952, making it 73 years old at the 2025 inventory.
• It carries about 78 vehicles a day (traffic count year 2011).
• Its listed owner is the county highway agency.
• It is one of 128 of the 202 inventoried bridges in Eaton County rated fair (63.4%); 11 (5.4%) 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 May 2023, 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 → (42.60287, -84.71934)

Component ratings

Bridge details

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

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