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.

Total bridges

157

Public highway bridges in Roberts County

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.

1900s

1
1920s

5
1930s

21
1940s

16
1950s

12
1960s

18
1970s

26
1980s

27
1990s

6
2000s

9
2010s

9
2020s

7

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.

Bridge inventory size and condition shares for Roberts County and the 5 South Dakota counties closest to it in inventory size
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 157 Good 36 Fair 83 Poor 38

Good-condition bridges (36)

Sort:

Roberts County Bridge Snapshot

Condition distribution

Roberts County's Poor-condition bridges carry 3,868 vehicle crossings a day

47.8% of Roberts County's bridges have passed the 50-year mark

One structure carries 64.6% of the county's Poor-condition bridge traffic

How Roberts County compares with South Dakota's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (36)

IRR 144 ST

456TH AVENUE

112th Street

459th Avenue

459th Avenue

127th Street

466th Avenue

SD015

467th Avenue

461st Street

122nd Street

474th Avenue

130th Street

IRR SD127

IRR I029 S

129th Street

469th Avenue

IRR SD010

110th Street

451st Avenue

467th Avenue

IRR SD127

470th Avenue

127th Street

112th Street

465th Avenue

IRR BIA RTE 121

456th Avenue

451st Avenue

455th Avenue

463rd Avenue

IRR SD010

127th Street

465th Avenue

SD015

471st Avenue

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