South Dakota bridge conditions
5,883 inventoried bridges · 945 rated poor · county by county
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 945 of South Dakota's 5,883 inventoried bridges are rated in poor condition (16.1%) in the 2025 National Bridge Inventory, as of .
- 2,038 bridges (34.6%) are rated good and 2,900 (49.3%) fair.
- The national poor rate is about 6.7%; South Dakota is above it (see all states ranked).
- The busiest poor-rated bridge in the state is US012 over Moccasin Ck in Brown County, carrying about 21,635 vehicles a day.
By the measure that matters most - the most traffic on a poor rating - it is US012 over Moccasin Ck in Brown County, built 1954, carrying about 21,635 vehicles a day. That is a repair-priority flag, not a collapse warning: what a poor rating does and does not mean. See the worst bridge in every state.
Good 34.6% · Fair 49.3% · Poor 16.1% of 5,883 bridges
Bridge conditions by county
Sorted by the number of poor-rated bridges. Click any county for its full bridge list.
The 25 busiest poor-rated bridges in South Dakota
Frequently asked questions
How many bridges in South Dakota are in poor condition?
945 of South Dakota's 5,883 inventoried highway bridges are rated in poor condition (16.1%) in the 2025 National Bridge Inventory. 'Poor' is FHWA's classification for a bridge whose deck, superstructure, or substructure is rated 4 or lower on the 0-9 scale; it was formerly called 'structurally deficient'.
Are the poor-rated bridges in South Dakota safe to drive on?
A poor rating flags advanced deterioration that needs repair or close monitoring; it does not by itself mean a bridge is unsafe. Bridges judged unsafe are closed or restricted to lighter loads by the owner. Inspections continue on all open bridges, generally at least every 24 months under the National Bridge Inspection Standards.
Source: FHWA National Bridge Inventory, 2025 vintage, reported by the South Dakota DOT.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.