Sully County Bridge Report Card
Sully County scores 45 out of 100 on BridgeLookup's Bridge Condition Exposure Score, based on FHWA National Bridge Inventory records.
Sully County, South Dakota
Sully County has 31 bridges in the National Bridge Inventory, with 6 rated poor and 2 rated scour-critical. Its poor-condition share of 19.4% is above the 16.1% statewide average. Poor-condition bridges carry about 214 daily vehicle crossings.
Quote-Ready Local Facts
Copyable Facts for Reporters
BridgeLookup.com gives Sully County a Bridge Condition Exposure Score of 45/100 (F). The county has 31 bridges in the National Bridge Inventory, including 6 in poor condition and 2 rated scour-critical. Poor-condition bridges carry about 214 daily vehicle crossings. Poor condition does not mean unsafe; bridges judged unsafe are closed or restricted by transportation agencies.
How the Score Breaks Down
| Factor | Weight | County Value | Penalty |
|---|---|---|---|
| Poor-condition bridge share | 40 | 19.4% | 38.7 |
| Poor-condition traffic exposure | 25 | 3.9% of measured traffic | 2.9 |
| Scour-critical bridge share | 20 | 6.5% | 12.9 |
| Average age vs national baseline | 10 | 47 years vs 48 nationally | 0.0 |
| Traffic-data completeness | 5 | 5,500 measured daily crossings | 0.0 |
Score = 100 minus weighted penalties. The score is a comparative research signal, not an official safety rating. Read the full methodology.
County Comparisons
| County Poor-Condition Share | 19.4% |
| State Poor-Condition Share | 16.1% |
| National Poor-Condition Share | 6.7% |
| County Scour-Critical Share | 6.5% |
| Average Bridge Age | 47 years |
| Poor-Condition Traffic Exposure | 214 vehicles/day |
Bridges to Watch
Top Bridges to Watch in Sully County
| Bridge | Reason | Condition | Daily Traffic | Year Built |
|---|---|---|---|---|
| 188 Street over Ck | Poor condition + traffic exposure | Poor | 75 | 1964 |
| 315 Avenue over Medicine Ck | Poor condition + traffic exposure | Poor | 64 | 1956 |
| 320 Avenue over Ck | Poor condition + traffic exposure | Poor | 25 | 1961 |
| 301 Avenue over Okobojo Creek | Poor condition + traffic exposure | Poor | 20 | 1961 |
| 302 Avenue over Okobojo Ck | Poor condition + traffic exposure | Poor | 20 | 1962 |
| 195 Street over Medicine Knoll Ck | Poor condition + traffic exposure | Poor | 10 | 1913 |
| Sd1804 over Okobojo Ck | Scour-critical foundation rating | Fair | 632 | 1972 |
| 291 Avenue over Okobojo Ck | Scour-critical foundation rating | Fair | 250 | 1936 |
| Us083 over Okobojo Ck | High traffic | Good | 1,490 | 1998 |
| 185 ST over Ck | High traffic | Good | 760 | 2017 |
Important safety note
Poor condition does not mean a bridge is unsafe. It means at least one major component has significant deterioration and the bridge is a priority for maintenance, repair, or replacement. Bridges judged unsafe are closed or restricted by transportation agencies.