Bridge conditions in Lyman County, South Dakota
114 inventoried bridges · 12 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
Lyman County has 12 bridges rated poor out of 114 inventoried, a 10.5% share that puts it well above the national rate of about 7%.
- 12 of the 114 bridges in Lyman County, South Dakota, are rated in poor condition (10.5%) in the 2025 National Bridge Inventory, as of .
- 46 bridges (40.4%) are rated good and 56 (49.1%) fair.
- The median Lyman County bridge was built in 1971.
- The busiest poor-rated bridge is I090 Wf over R&w RR (built 1953), carrying about 2,622 vehicles a day.
Good 40.4% · Fair 49.1% · Poor 10.5% of 114 bridges
Bridges rated poor
Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I090 Wf over R&w RR | 1953 | 2,622 | Poor |
| Irr Bia Rte 5 over Counselor Creek | 1965 | 663 | Poor |
| 241ST Street over Medicine Creek | 1930 | 55 | Poor |
| 241ST Street over Trib. to Medicine Creek | 1930 | 45 | Poor |
| 318TH Avenue over Creek | 1930 | 24 | Poor |
| River Road over Creek | 1965 | 16 | Poor |
| 338TH Avenue over Waterhole Creek | 1950 | 15 | Poor |
| 304TH Avenue over Creek | 1966 | 10 | Poor |
| Shades Road over Creek | 1955 | 10 | Poor |
| County Rd over Ck | 1945 | 10 | Poor |
| 327TH Avenue over Creek | 1940 | 10 | Poor |
| County Rd over Ck | 1950 | 10 | Poor |
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I090 W over SD090 L | 1971 | 4,382 | Good |
| I090 E over SD090 L | 1971 | 4,382 | Good |
| I090 W over SD273 | 1970 | 3,955 | Fair |
| I090 E over SD273 | 1970 | 3,955 | Fair |
| I090 W over 319 Ave | 1971 | 3,955 | Fair |
| I090 E over 319 Ave | 1971 | 3,955 | Fair |
| I090 W over 321 Ave | 1971 | 3,852 | Fair |
| I090 E over 321 Ave | 1971 | 3,852 | Fair |
| I090 W over 324 Ave | 1971 | 3,852 | Fair |
| I090 E over 324 Ave | 1971 | 3,852 | Fair |
Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.
All of South Dakota: South Dakota bridge conditions by county · every download on the data page.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.