County profile · official public datasets

Johnson County, IA

372 public highway bridges tracked in the FHWA National Bridge Inventory: 39.5% rated Good, 50.3% Fair, 10.2% Poor.

372
Public bridges
39.5%
Good condition
10.2%
Poor condition

The verdict

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

Johnson County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 21%
lowest Poor share in state
10.2%
Poor-condition share
372
public highway bridges
1979
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.

Johnson County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Johnson County ranks #21 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 10.2%). Johnson County, Iowa contains 372 public highway bridges. Roughly 39.5% are rated “Good,” 50.3% “Fair,” and 10.2% “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

372

Public highway bridges in Johnson County

Good condition

39.5%

147 of 372 rated 7-9

Fair condition

50.3%

187 of 372 rated 5-6

Poor condition

10.2%

38 of 372 rated 4 or below

In-state Poor-share rank

#21 of 99

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

Condition distribution

Share of 372 NBI-tracked bridges by lowest applicable component rating.

Good
39.5% (147)
Fair
50.3% (187)
Poor
10.2% (38)

Johnson County's Poor-condition bridges carry 55,995 vehicle crossings a day

That is 3.5% of the county's reported daily bridge traffic on 10.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,474 crossings a day against 5,176 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 372 of 372 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

41.9% of Johnson County's bridges have passed the 50-year mark

156 of the 372 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 39.5% 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 25% of the county's Poor-condition bridge traffic

GILBERT ST over RALSTON CREEK, built 1972, carries 14,025 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 55,995 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Johnson County's bridges were built

372 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1970s, when 71 of the county's bridges still in the inventory were built, which is 19.1% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1979) matches the Iowa average (1979).

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

How Johnson County compares with Iowa's closest counties by inventory size

The 5 Iowa counties nearest Johnson County in number of bridges, with their condition splits. Its 10.2% Poor share is the 3rd-lowest of these 6. Its average build year of 1979 against a peer-group mean of 1982 is in line with the group.

Showing the 5 closest of 98 Iowa counties eligible for comparison.

Bridge inventory size and condition shares for Johnson County and the 5 Iowa counties closest to it in inventory size
County Bridges Poor
Jasper County 382 29.1%
Benton County 374 23%
Clinton County 372 3%
Johnson County (this page) 372 10.2%
Fayette County 362 24.6%
Dubuque County 346 8.7%

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

Similar inventory size

Nearest county inventories outside IA (372 bridges here).

Similar average build year

Nearest mean year-built outside IA (1979 here).

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

All 372 Good 147 Fair 187 Poor 38

Good-condition bridges (147)

HALF MOON AVE

Good

Over: I-80

2.8 mi. W of Jct. I-380, Johnson, IA

Built 1963 Load: 18.7 t ADT: 410

1ST AVE

Good

Over: RALSTON CREEK S. BRANCH

079061300, Johnson, IA

Built 1997 Load: 20.1 t ADT: 14,992

OAKDALE BLVD

Good

Over: MUDDY CREEK

000000000, Johnson, IA

Built 1996 Load: 24.5 t ADT: 5,803

FM SAND RD

Good

Over: STREAM

078060204, Johnson, IA

Built 2005 Load: 25.1 t ADT: 2,620

FM SW BLK DIMND

Good

Over: OLD MANS CREEK

000000000, Johnson, IA

Built 2009 Load: 25.6 t ADT: 670

HWY 965

Good

Over: IOWA RIVER

081072206, Johnson, IA

Built 1956 Load: 26.2 t ADT: 4,280

FM F-12

Good

Over: I-380 & US 218

2.9 MI. S OF CO RD E70., Johnson, IA

Built 1972 Load: 26.8 t ADT: 6,800

US 6

Good

Over: STREAM

1.5 mi. W of Jct. SR 965, Johnson, IA

Built 1960 Load: 27.1 t ADT: 10,300

LOCAL RD

Good

Over: I-380

5.6 MI. N OF JCT. I-80, Johnson, IA

Built 1971 Load: 28.0 t ADT: 131

IA 1 SB

Good

Over: I-80

AT JCT. I-80, Johnson, IA

Built 1962 Load: 28.7 t ADT: 9,350

IA 1 NB

Good

Over: I-80

AT JCT. I-80, Johnson, IA

Built 1962 Load: 29.3 t ADT: 9,350

NW BAXTER AVE

Good

Over: KNAPP CREEK

081080604, Johnson, IA

Built 1995 Load: 30.7 t ADT: 15

DANE RD

Good

Over: US 218

0.8 mi. S of Jct. IA #1, Johnson, IA

Built 1983 Load: 32.1 t ADT: 630

EAGLE AVE

Good

Over: CLEAR CREEK

080082308, Johnson, IA

Built 1993 Load: 32.2 t ADT: 15

SW NAPLES AVE

Good

Over: BR OLD MAN CR

078060802, Johnson, IA

Built 1997 Load: 32.3 t ADT: 102

SW EAGLE AVENUE

Good

Over: F OLD MANS CREEK

079081004, Johnson, IA

Built 2002 Load: 32.3 t ADT: 51

1ST AVENUE

Good

Over: MUDDY CREEK

080063204, Johnson, IA

Built 1988 Load: 32.3 t ADT: 6,625

2ND AVENUE

Good

Over: S BRANCH RALSTON CREEK

079061400, Johnson, IA

Built 2022 Load: 32.4 t ADT: 158

IA 1

Good

Over: OLD MANS CREEK

1.5 mi. S of SR F52, Johnson, IA

Built 2020 Load: 32.4 t ADT: 4,890

IA 1

Good

Over: OLD WOMANS CREEK

0.6 mi. N of SR F52, Johnson, IA

Built 2020 Load: 32.4 t ADT: 4,890

IA 1 NB

Good

Over: RALSTON CREEK

2.3 MI. S. OF I-80, Johnson, IA

Built 2019 Load: 32.4 t ADT: 2,850

I 80 EB

Good

Over: CLEAR CREEK

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2023 Load: 32.4 t ADT: 13,450

I 80 WB

Good

Over: CLEAR CREEK

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 13,450

I 80 EB

Good

Over: IOWA RIVER

3.0 MI. W OF JCT. IA 1, Johnson, IA

Built 1960 Load: 32.4 t ADT: 32,050

WAPSI AVE

Good

Over: I 80

1.2 mi. E of Jct. SR F44, Johnson, IA

Built 2023 Load: 32.4 t ADT: 220

F46 IWV RD

Good

Over: OLD WOMANS CR

079081401, Johnson, IA

Built 2005 Load: 32.4 t ADT: 480

PRENTISS ST

Good

Over: RALSTON CREEK

079061500, Johnson, IA

Built 2020 Load: 32.4 t ADT: 1,664

I 380 NB

Good

Over: I 80

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2021 Load: 32.4 t ADT: 9,650

I80 WB TO I380 NB

Good

Over: CLEAR CREEK

I-80/I-380/US 218 INTERCH, Johnson, IA

Built 2021 Load: 32.4 t ADT: 13,800

I 380 NB

Good

Over: CLEAR CREEK

0.5 MI. N OF JCT. 80, Johnson, IA

Built 2021 Load: 32.4 t ADT: 18,000

I 380 SB

Good

Over: CLEAR CREEK

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 18,000

I 380 NB

Good

Over: IAIS RR

0.7 MI. N OF JCT. I-80, Johnson, IA

Built 2021 Load: 32.4 t ADT: 26,550

I 380 SB

Good

Over: IAIS RR

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 26,550

I 380 NB

Good

Over: US 6

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2021 Load: 32.4 t ADT: 26,550

I 380 SB

Good

Over: US 6

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 26,550

FOREVERGREEN RD

Good

Over: I 380

2 MI. N OF I-80, Johnson, IA

Built 2017 Load: 32.4 t ADT: 2,027

US218 NB TO I80 EB

Good

Over: CLEAR CREEK

I-80/I-380/US 218 INTERCH, Johnson, IA

Built 2021 Load: 32.4 t ADT: 4,830

US 218 IA 27 NB

Good

Over: I380 SB TO I80 EB RAMP F

I-80 I-380 US 218 INTER, Johnson, IA

Built 2021 Load: 32.4 t ADT: 9,650

US 218 IA 27 SB

Good

Over: I380 SB TO I80 EB RAMP F

I-80 I-380 US 218 INTER, Johnson, IA

Built 2021 Load: 32.4 t ADT: 9,650

I 380 NB

Good

Over: I 80 WB RAMPS

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2021 Load: 32.4 t ADT: 9,650

I 380 SB

Good

Over: I 80 WB RAMPS

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2021 Load: 32.4 t ADT: 9,650

I 80 EB

Good

Over: I 80 WB TO US 218 SB

I-80/I-380 INTERCHANGE, Johnson, IA

Built 2023 Load: 32.4 t ADT: 13,450

I 80 WB

Good

Over: I 80 WB TO US 218 SB

I-80 / I-380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 13,450

I380 SB TO I80 EB

Good

Over: CLEAR CREEK

I80/I380 INTERCHANGE, Johnson, IA

Built 2022 Load: 32.4 t ADT: 14,400

560TH ST

Good

Over: BR DEER CREEK

078083401, Johnson, IA

Built 1999 Load: 32.7 t ADT: 70

SW 360TH ST

Good

Over: N BR OLD MANS CR

079080903, Johnson, IA

Built 1998 Load: 32.7 t ADT: 35

LOCAL

Good

Over: SMALL STREAM

077052101, Johnson, IA

Built 1999 Load: 32.7 t ADT: 60

MORMAN TREK BLV

Good

Over: WILLOW CREEK

079062100, Johnson, IA

Built 2005 Load: 32.7 t ADT: 5,200

OAKDALE BLVD

Good

Over: MUDDY CREEK

080063304, Johnson, IA

Built 2009 Load: 32.7 t ADT: 4,020

SWISHERVIEW DR.

Good

Over: SMALL STREAM

000000000, Johnson, IA

Built 1900 Load: 32.7 t ADT: 1,168

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.