Total bridges
157
Public highway bridges in Roberts County
County profile · official public datasets
Roberts County, SD
157 public highway bridges tracked in the FHWA National Bridge Inventory: 22.9% rated Good, 52.9% Fair, 24.2% Poor.
- 157
- Public bridges
- 22.9%
- Good condition
- 24.2%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Roberts County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.
- 52nd
- of 66 on Poor share
- 24.2%
- Poor-condition share
- 157
- public highway bridges
- 1970
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
Roberts County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Roberts County ranks #52 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 24.2%). Roberts County, South Dakota contains 157 public highway bridges. Roughly 22.9% are rated “Good,” 52.9% “Fair,” and 24.2% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
22.9%
36 of 157 rated 7-9
Fair condition
52.9%
83 of 157 rated 5-6
Poor condition
24.2%
38 of 157 rated 4 or below
In-state Poor-share rank
#52 of 66
Among South Dakota counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 157 NBI-tracked bridges by lowest applicable component rating.
Good 22.9% (36)
Fair 52.9% (83)
Poor 24.2% (38)
Roberts County's Poor-condition bridges carry 3,868 vehicle crossings a day
That is 2.5% of the county's reported daily bridge traffic on 24.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 102 crossings a day against 722 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 157 of 157 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
47.8% of Roberts County's bridges have passed the 50-year mark
75 of the 157 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 22.9% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
One structure carries 64.6% of the county's Poor-condition bridge traffic
455th Avenue over Big Sioux River, built 1939, carries 2,500 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 38-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 3,868 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Roberts County's bridges were built
157 bridges with a recorded construction year, grouped by decade
- 1900s 1
1900–1909
1 bridges
- 1920s 5
1920–1929
5 bridges
- 1930s
1930–1939
21 bridges
- 1940s
1940–1949
16 bridges
- 1950s
1950–1959
12 bridges
- 1960s
1960–1969
18 bridges
- 1970s
1970–1979
26 bridges
- 1980s
1980–1989
27 bridges
- 1990s 6
1990–1999
6 bridges
- 2000s 9
2000–2009
9 bridges
- 2010s 9
2010–2019
9 bridges
- 2020s 7
2020–2029
7 bridges
What this shows Construction peaked in the 1980s, when 27 of the county's bridges still in the inventory were built, which is 17.2% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1970, 5 years older than the South Dakota average of 1975.
How Roberts County compares with South Dakota's closest counties by inventory size
The 5 South Dakota counties nearest Roberts County in number of bridges, with their condition splits. Its 24.2% Poor share is the 5th-lowest of these 6. Its average build year of 1970 against a peer-group mean of 1973 is in line with the group.
Showing the 5 closest of 65 South Dakota counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Brown County | 170 | 32.9% | 55.3% | 11.8% | 1983 |
| Union County | 170 | 31.2% | 49.4% | 19.4% | 1975 |
| Hutchinson County | 161 | 32.9% | 50.9% | 16.1% | 1974 |
| Roberts County (this page) | 157 | 22.9% | 52.9% | 24.2% | 1970 |
| Beadle County | 152 | 19.1% | 47.4% | 33.6% | 1955 |
| Butte County | 143 | 30.8% | 57.3% | 11.9% | 1976 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Roberts County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for Roberts County, both outside South Dakota so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside SD (157 bridges here).
- Lowndes County, AL · 157 bridges
- Jefferson County, IA · 157 bridges
- Franklin County, MS · 157 bridges
- Washington County, MO · 157 bridges
Similar average build year
Nearest mean year-built outside SD (1970 here).
- Hamilton County, OH · avg 1970 · 783 bridges
- Yavapai County, AZ · avg 1970 · 543 bridges
- Garfield County, OK · avg 1970 · 504 bridges
- San Luis Obispo County, CA · avg 1970 · 401 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (157)
104th Street
PoorOver: Creek
4.5E & 1N of Rosholt, Roberts, SD
Built 1940 Load: 12.2 t ADT: 25
468th Avenue
PoorOver: Creek
1.8S & 0.3E of Wilmot, Roberts, SD
Built 1901 Load: 14.5 t ADT: 50
467th Avenue
PoorOver: Creek
0.6N of Wilmot, Roberts, SD
Built 1968 Load: 16.3 t ADT: 165
476th Avenue
PoorOver: Big Slough Creek
3E & 1.4N of Rosholt, Roberts, SD
Built 1930 Load: 16.3 t ADT: 22
477th Avenue
PoorOver: Big Slough Creek
4E & 1.1N of Rosholt, Roberts, SD
Built 1955 Load: 16.3 t ADT: 22
463rd Avenue
PoorOver: Creek
3.8S & 4W of Wilmot, Roberts, SD
Built 1966 Load: 16.5 t ADT: 30
104th Street
PoorOver: Little Minnesota River
1W & 1.5N of Claire City, Roberts, SD
Built 1967 Load: 18.3 t ADT: 35
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.