County profile · official public datasets

Shelby County, IL

335 public highway bridges tracked in the FHWA National Bridge Inventory: 56.4% rated Good, 36.4% Fair, 7.2% Poor.

335
Public bridges: 56.4%
Good condition: 7.2%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Shelby County posts a better-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 44%
lowest Poor share in state: 7.2%
Poor-condition share: 335
public highway bridges: 1978
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.

Shelby County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Shelby County ranks #45 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.2%). Shelby County, Illinois contains 335 public highway bridges. Roughly 56.4% are rated “Good,” 36.4% “Fair,” and 7.2% “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

335

Public highway bridges in Shelby County

Good condition

56.4%

189 of 335 rated 7-9

Fair condition

36.4%

122 of 335 rated 5-6

Poor condition

7.2%

24 of 335 rated 4 or below

In-state Poor-share rank

#45 of 102

Among Illinois counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 335 NBI-tracked bridges by lowest applicable component rating.

Good

56.4% (189)

Fair

36.4% (122)

Poor

7.2% (24)

Shelby County's Poor-condition bridges carry 3,975 vehicle crossings a day

That is 2.7% of the county's reported daily bridge traffic on 7.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 166 crossings a day against 292 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 335 of 335 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

32.8% of Shelby County's bridges have passed the 50-year mark

110 of the 335 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 56.4% 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 34% of the county's Poor-condition bridge traffic

TR 62(N. MAIN ST) over LONG GROVE CREEK, built 1953, carries 1,350 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 24-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 3,975 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

27
1910s

5
1920s

10
1930s

21
1940s

5
1950s

14
1960s

21
1970s

14
1980s

60
1990s

61
2000s

57
2010s

33
2020s

6

What this shows Construction peaked in the 1990s, when 61 of the county's bridges still in the inventory were built, which is 18.2% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year (1978) matches the Illinois average (1979).

How Shelby County compares with Illinois's closest counties by inventory size

The 5 Illinois counties nearest Shelby County in number of bridges, with their condition splits. Its 7.2% Poor share is the 3rd-lowest of these 6. Its average build year of 1978 against a peer-group mean of 1981 is in line with the group.

Showing the 5 closest of 101 Illinois counties eligible for comparison.

Bridge inventory size and condition shares for Shelby County and the 5 Illinois counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
DuPage County	344	37.5%	54.4%	8.1%	1985
Stephenson County	342	61.1%	36.3%	2.6%	1977
Kane County	336	48.2%	45.5%	6.3%	1986
Shelby County (this page)	335	56.4%	36.4%	7.2%	1978
Pike County	330	23.9%	66.1%	10%	1979
Henry County	328	49.4%	39.6%	11%	1978

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 Shelby 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 Shelby County, both outside Illinois so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IL (335 bridges here).

Washington County, KS · 335 bridges
Iredell County, NC · 335 bridges
Grand Forks County, ND · 335 bridges
Jefferson County, AR · 336 bridges

Similar average build year

Nearest mean year-built outside IL (1978 here).

Orange County, CA · avg 1978 · 1,164 bridges
Sumner County, KS · avg 1978 · 659 bridges
Allen County, IN · avg 1978 · 613 bridges
Buncombe County, NC · avg 1978 · 555 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 335 Good 189 Fair 122 Poor 24

Good-condition bridges (189)

Sort:

Shelby County Bridge Snapshot

Condition distribution

Shelby County's Poor-condition bridges carry 3,975 vehicle crossings a day

32.8% of Shelby County's bridges have passed the 50-year mark

One structure carries 34% of the county's Poor-condition bridge traffic

How Shelby County compares with Illinois'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 (189)

TR 72 A

TR 249

TR 408

TR 29

TR 197

TR 352

FAS 1631

TR 180

TR 183

TR 14

TR 354C

TR 128

TR 121

TR 140

TR 1

TR 69

TR 338

TR 173

CH 23

CH 23

TR 245

TR 112A

TR 112B

TR 423 A

TR 57

TR 320

TR 205

TR 234A

TR 133

TR 140

TR 243

TR 74

TR 335A

TR 283A

TR 367

TR 183

CH 6 (FAS 653)

TR 217

TR 336A

TR 159

TR 303

TR 231

TR 373

CH 30

CH 12

TR 431

TR 272

TR 60

TR 361

TR 431A

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