I090 E over 300 Ave

Lyman County, South Dakota · rated Fair in the 2025 National Bridge Inventory

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

• I090 E over 300 Ave in Lyman County, South Dakota, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
• It was built in 1970, making it 55 years old at the 2025 inventory.
• It carries about 3,787 vehicles a day (traffic count year 2024).
• Its listed owner is the state highway agency.
• It is one of 56 of the 114 inventoried bridges in Lyman County rated fair (49.1%); 12 (10.5%) are rated poor.
• 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 → (43.90351, -100.16586)

Component ratings

Bridge details

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

Busiest bridges in Lyman County

All bridges nearby: Lyman County, SD bridge conditions · every bridge in Lyman County · South Dakota bridges.

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