Total bridges
372
Public highway bridges in Johnson County
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.
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
- 1900s 15
1900–1909
15 bridges
- 1910s 9
1910–1919
9 bridges
- 1920s 7
1920–1929
7 bridges
- 1930s 10
1930–1939
10 bridges
- 1940s 3
1940–1949
3 bridges
- 1950s 22
1950–1959
22 bridges
- 1960s
1960–1969
52 bridges
- 1970s
1970–1979
71 bridges
- 1980s
1980–1989
40 bridges
- 1990s
1990–1999
46 bridges
- 2000s
2000–2009
35 bridges
- 2010s 24
2010–2019
24 bridges
- 2020s
2020–2029
38 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).
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.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Jasper County | 382 | 38.5% | 32.5% | 29.1% | 1977 |
| Benton County | 374 | 34.2% | 42.8% | 23% | 1984 |
| Clinton County | 372 | 66.7% | 30.4% | 3% | 1986 |
| Johnson County (this page) | 372 | 39.5% | 50.3% | 10.2% | 1979 |
| Fayette County | 362 | 35.1% | 40.3% | 24.6% | 1974 |
| Dubuque County | 346 | 50.6% | 40.8% | 8.7% | 1989 |
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).
- Harper County, KS · 372 bridges
- Harvey County, KS · 372 bridges
- Wharton County, TX · 372 bridges
- Solano County, CA · 373 bridges
Similar average build year
Nearest mean year-built outside IA (1979 here).
- Pima County, AZ · avg 1979 · 1,150 bridges
- Jefferson County, KY · avg 1979 · 662 bridges
- Spartanburg County, SC · avg 1979 · 638 bridges
- McPherson County, KS · avg 1979 · 586 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (187)
SW 360TH ST
FairOver: N BR OLD MANS CR
079080801, Johnson, IA
Built 1915 Load: 8.5 t ADT: 35
OASIS RD
FairOver: SMALL
079052402, Johnson, IA
Built 1979 Load: 10.4 t ADT: 61
FM CEDAR CK RD
FairOver: SMALL STREAM
081050101, Johnson, IA
Built 1946 Load: 10.4 t ADT: 160
VEGA RD
FairOver: SMALL STREAM
081050304, Johnson, IA
Built 1985 Load: 11.9 t ADT: 45
FM
FairOver: I-80
1.7 mi. W of Jct. SR X30, Johnson, IA
Built 1960 Load: 12.5 t ADT: 70
US 6
FairOver: STREAM
4.0 mi. E of Jct. SR W38., Johnson, IA
Built 1923 Load: 12.6 t ADT: 5,200
EAGLE AVE
FairOver: I-80
6.1 MI. W OF JCT. I-380, Johnson, IA
Built 1963 Load: 14.5 t ADT: 140
VINCENT AVE SE
FairOver: STREAM
078051004, Johnson, IA
Built 1970 Load: 14.5 t ADT: 20
NW CHAMBERS AVE
FairOver: STREAM
081080904, Johnson, IA
Built 1972 Load: 14.5 t ADT: 92
500TH ST SE
FairOver: STREAM
078051301, Johnson, IA
Built 1971 Load: 14.8 t ADT: 35
FM
FairOver: OLD MANS CREEK
079083504, Johnson, IA
Built 1969 Load: 16.2 t ADT: 700
3RD ST
FairOver: SMALL STREAM
000000000, Johnson, IA
Built 1980 Load: 16.5 t ADT: 260
400TH ST
FairOver: WAPSINONOE CREEK
079052301, Johnson, IA
Built 1977 Load: 16.8 t ADT: 80
SIXTH AVE
FairOver: RALSTON CREEK S. BRANCH
079061400, Johnson, IA
Built 1930 Load: 17.0 t ADT: 133
FM
FairOver: PICAYUNE CR
078072906, Johnson, IA
Built 1976 Load: 17.1 t ADT: 240
NE 340TH ST
FairOver: STREAM
079050201, Johnson, IA
Built 1952 Load: 17.1 t ADT: 51
FM 310TH ST
FairOver: STREAM
080052503, Johnson, IA
Built 1900 Load: 17.1 t ADT: 60
TAFT AVE
FairOver: STREAM
081051804, Johnson, IA
Built 1970 Load: 17.1 t ADT: 31
FM JOHNS-IOWA R
FairOver: STREAM
081080602, Johnson, IA
Built 1966 Load: 17.1 t ADT: 730
SE WHITE OAK AV
FairOver: BIG SLOUGH CR
078051104, Johnson, IA
Built 1920 Load: 18.0 t ADT: 35
US 6
FairOver: DRAINAGE DITCH
1.8 mi. E of Jct. SR W38, Johnson, IA
Built 1953 Load: 18.1 t ADT: 5,200
US 6
FairOver: STREAM
3.1 MI. E OF JCT. SR W38, Johnson, IA
Built 1953 Load: 18.1 t ADT: 5,200
US 6
FairOver: PIG RUN CREEK
4.1 mi. E of Jct. SR W-38, Johnson, IA
Built 1923 Load: 18.1 t ADT: 5,200
140TH ST NE
FairOver: STREAM
081071603, Johnson, IA
Built 1977 Load: 18.2 t ADT: 663
SW OBSERVATORY
FairOver: BRANCH OF CROOKED CREEK
078062804, Johnson, IA
Built 1984 Load: 18.3 t ADT: 122
US 6
FairOver: SNYDER CREEK
0.7 mi. W of SR X14, Johnson, IA
Built 1957 Load: 19.0 t ADT: 5,300
SE 660TH ST
FairOver: PRAIRIE CR
077052901, Johnson, IA
Built 1930 Load: 19.4 t ADT: 26
W 295TH ST
FairOver: BR CLEAR CR
080081903, Johnson, IA
Built 1977 Load: 19.4 t ADT: 60
140TH ST NW
FairOver: KNAPP CREEK
081081601, Johnson, IA
Built 1987 Load: 19.4 t ADT: 50
US 6
FairOver: RALSTON CREEK
0.3 MI. E OF E JCT. IA #1, Johnson, IA
Built 1957 Load: 20.9 t ADT: 27,000
PRAIRIEDUCHIEN RD
FairOver: I 80
1.3 MI. W OF JCT. IA 1, Johnson, IA
Built 1962 Load: 20.9 t ADT: 4,310
FM MORSE RD
FairOver: RAPID CR
080050903, Johnson, IA
Built 1930 Load: 21.2 t ADT: 1,220
US 6
FairOver: IOWA RIVER
0.2 MI. E OF E JCT. IA 1, Johnson, IA
Built 1957 Load: 21.4 t ADT: 27,000
FM-BLACKHAWK AV
FairOver: CLEAR CREEK
080082904, Johnson, IA
Built 1995 Load: 21.6 t ADT: 1,200
COLLEGE ST
FairOver: RALSTON CREEK
079061000, Johnson, IA
Built 1971 Load: 21.7 t ADT: 1,940
OAKCRESTHILL RD
FairOver: DRAINAGE DITCH
078061502, Johnson, IA
Built 2003 Load: 21.9 t ADT: 1,670
WATER STREET NE
FairOver: WEST HOOSIER CREEK
0810703, Johnson, IA
Built 2010 Load: 22.3 t ADT: 49
WAPSIE RD
FairOver: STREAM
080052106, Johnson, IA
Built 1965 Load: 22.5 t ADT: 102
MUSCATINE AVE
FairOver: RALSTON CREEK
079061400, Johnson, IA
Built 1979 Load: 22.8 t ADT: 7,256
FM MAHAFFY BR R
FairOver: STREAM
081062806, Johnson, IA
Built 2000 Load: 23.7 t ADT: 3,730
TAFT AVE
FairOver: STREAM
079053202, Johnson, IA
Built 1966 Load: 24.5 t ADT: 734
MUSCATINE AVE
FairOver: RALSTON CK S BRANCH
079061400, Johnson, IA
Built 1972 Load: 24.5 t ADT: 9,524
SW BLACKHAWK AV
FairOver: MILLER CREEK
078081904, Johnson, IA
Built 2004 Load: 24.6 t ADT: 11
NB I-380
FairOver: IOWA RIVER
7.9 MI. N OF JCT I-80, Johnson, IA
Built 1972 Load: 24.7 t ADT: 27,200
FM SUTLIFF RD
FairOver: CEDAR RIVER
081051105, Johnson, IA
Built 1983 Load: 24.9 t ADT: 480
SW OBSERVTY AVE
FairOver: OLD MANS CREEK
078062105, Johnson, IA
Built 1980 Load: 25.1 t ADT: 290
FM SAND RD
FairOver: SNYDER CREEK
078060204, Johnson, IA
Built 1964 Load: 25.3 t ADT: 2,620
SB I-380
FairOver: IOWA RIVER
7.9 MI. N OF JCT. I-80, Johnson, IA
Built 1972 Load: 25.4 t ADT: 27,200
FM 660TH ST
FairOver: RICHEY CREEK
077052501, Johnson, IA
Built 1979 Load: 25.5 t ADT: 35
FM 120TH ST
FairOver: HOOSIER CREEK
081060509, Johnson, IA
Built 1900 Load: 26.2 t ADT: 1,500
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.