Union County Bridge Report Card
Union County scores 51 out of 100 on BridgeLookup's Bridge Condition Exposure Score, based on FHWA National Bridge Inventory records.
Union County, South Dakota
Union County has 169 bridges in the National Bridge Inventory, with 41 rated poor and 4 rated scour-critical. Its poor-condition share of 24.3% is above the 16.1% statewide average. Poor-condition bridges carry about 11,588 daily vehicle crossings.
Quote-Ready Local Facts
Copyable Facts for Reporters
BridgeLookup.com gives Union County a Bridge Condition Exposure Score of 51/100 (F). The county has 169 bridges in the National Bridge Inventory, including 41 in poor condition and 4 rated scour-critical. Poor-condition bridges carry about 11,588 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 | 24.3% | 40.0 |
| Poor-condition traffic exposure | 25 | 5.5% of measured traffic | 4.1 |
| Scour-critical bridge share | 20 | 2.4% | 4.7 |
| Average age vs national baseline | 10 | 49 years vs 48 nationally | 0.4 |
| Traffic-data completeness | 5 | 211,189 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 | 24.3% |
| State Poor-Condition Share | 16.1% |
| National Poor-Condition Share | 6.7% |
| County Scour-Critical Share | 2.4% |
| Average Bridge Age | 49 years |
| Poor-Condition Traffic Exposure | 11,588 vehicles/day |
Bridges to Watch
Top Bridges to Watch in Union County
| Bridge | Reason | Condition | Daily Traffic | Year Built |
|---|---|---|---|---|
| I029 N over 302 ST (fas 6372) | Poor condition + traffic exposure | Poor | 8,020 | 1960 |
| 48480 Co HWY 13 over Green Ck | Poor condition + traffic exposure | Poor | 500 | 1985 |
| 47400 302 St. over West Brule Ck | Poor condition + traffic exposure | Poor | 435 | 1960 |
| 30330 River Road over Ck | Poor condition + traffic exposure | Poor | 325 | 1972 |
| 31490 477th AVE over Br Brule Ck | Poor condition + traffic exposure | Poor | 300 | 1955 |
| 30999 477th AVE over Ck | Poor condition + traffic exposure | Poor | 300 | 1989 |
| 47580 302nd ST over East Brule Ck | Poor condition + traffic exposure | Poor | 270 | 1960 |
| 48050 311th ST over East Union Ck | Poor condition + traffic exposure | Poor | 110 | 1950 |
| 29895 Boyer AVE over Ck | Poor condition + traffic exposure | Poor | 70 | 1992 |
| 31490 475th ST over Brule Ck | Poor condition + traffic exposure | Poor | 60 | 1977 |
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.