County profile · official public datasets

Iron County, UT

70 public highway bridges tracked in the FHWA National Bridge Inventory: 10% rated Good, 88.6% Fair, 1.4% Poor.

70
Public bridges: 10%
Good condition: 1.4%
Poor condition

The verdict

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

Iron County pairs a better-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

Top 45%
lowest Poor share in state: 1.4%
Poor-condition share: 70
public highway bridges: 1977
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.

Iron County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Iron County ranks #13 of 29 Utah counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 1.4%). Iron County, Utah contains 70 public highway bridges. Roughly 10% are rated “Good,” 88.6% “Fair,” and 1.4% “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

Public highway bridges in Iron County

Good condition

10%

7 of 70 rated 7-9

Fair condition

88.6%

62 of 70 rated 5-6

Poor condition

1.4%

1 of 70 rated 4 or below

In-state Poor-share rank

#13 of 29

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

Condition distribution

Share of 70 NBI-tracked bridges by lowest applicable component rating.

Good

10% (7)

Fair

88.6% (62)

Poor

1.4% (1)

Iron County's Poor-condition bridges carry 50 vehicle crossings a day

That is 0% of the county's reported daily bridge traffic on 1.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 50 crossings a day against 9,483 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 69 of 70 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

61.4% of Iron County's bridges have passed the 50-year mark

43 of the 70 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 10% 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 100% of the county's Poor-condition bridge traffic

NFSR 30095 over DUCK CREEK, built 1973, carries 50 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 1-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 50 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

1
1930s

1
1940s

1
1950s

7
1960s

21
1970s

15
1980s

7
1990s

6
2000s

5
2010s

3
2020s

3

What this shows Construction peaked in the 1960s, when 21 of the county's bridges still in the inventory were built, which is 30% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1977, 7 years older than the Utah average of 1984.

How Iron County compares with Utah's closest counties by inventory size

The 5 Utah counties nearest Iron County in number of bridges, with their condition splits. Its 1.4% Poor share is the 2nd-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1979 is in line with the group.

Showing the 5 closest of 28 Utah counties eligible for comparison.

Bridge inventory size and condition shares for Iron County and the 5 Utah counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Duchesne County	84	26.2%	67.9%	6%	1984
Carbon County	73	19.2%	78.1%	2.7%	1974
Millard County	72	12.5%	86.1%	1.4%	1978
Iron County (this page)	70	10%	88.6%	1.4%	1977
Juab County	60	8.3%	88.3%	3.3%	1980
Beaver County	53	17%	79.2%	3.8%	1977

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

Similar inventory size

Nearest county inventories outside UT (70 bridges here).

Jefferson County, FL · 70 bridges
Jasper County, GA · 70 bridges
Treutlen County, GA · 70 bridges
Turner County, GA · 70 bridges

Similar average build year

Nearest mean year-built outside UT (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

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

All 70 Good 7 Fair 62 Poor 1

All bridges (70)

Sort:

Iron County Bridge Snapshot

Condition distribution

Iron County's Poor-condition bridges carry 50 vehicle crossings a day

61.4% of Iron County's bridges have passed the 50-year mark

One structure carries 100% of the county's Poor-condition bridge traffic

How Iron County compares with Utah's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (70)

CITY STREET

I-15 (SR-15) SBL

PAROWAN MAIN ST.

CNTY.ROAD-FAS# 370

WINDING ROAD

CO.RD.INTER X-ROAD

SR-56

CENTER STREET

I-15 (SR-15) NBL

I-15 (SR-15) SBL

I-15 (SR-15) NBL

COUNTY ROAD

CO.RD.-BIG FIELDS

I-15 (SR-15) NBL

I-15 (SR-15) SBL

CO.RD.-BUCKHORN FL

SR-14

SR-14

I-15 (SR-15) NBL

I-15 (SR-15) SBL

SR-130

Airport Rd

I-15 (SR-15) NBL

I-15 (SR-15) NBL

SR-130 SBL ONLY

I-15 (SR-15) SBL

600 SOUTH STREET

COUNTY ROAD

CO. RD.NW KANARRAV

SR-56

RD.TO HAMILTON FT.

I-15 (SR-15)NB&SB

COUNTY ROAD

Paint Shop Rd

COUNTY ROAD

WESTVIEW DRIVE

SR-271 INT. X-ROAD

SR-14

I-15 (SR-15) SBL

County Road

COUNTY RD.INT.X-RD

SR-14

SR-20 INT.X-ROAD

I-15(SR-15)NB&Ramp

3000 NORTH STREET

INTS.SR56-LUND HWY

SR-274 INT. X-ROAD

COUNTY ROAD

Aviation Way

I-15(SR-15)NB SB

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