Total bridges
590
Public highway bridges in Dane County
County profile · official public datasets
Dane County, WI
590 public highway bridges tracked in the FHWA National Bridge Inventory: 51.2% rated Good, 42.4% Fair, 6.4% Poor.
- 590
- Public bridges
- 51.2%
- Good condition
- 6.4%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Dane County posts a higher-than-median Poor-condition share among rated counties in the state across large county bridge inventory.
- 41st
- of 72 on Poor share
- 6.4%
- Poor-condition share
- 590
- public highway bridges
- 1987
- 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.
Dane County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Dane County ranks #41 of 72 Wisconsin counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.4%). Dane County, Wisconsin contains 590 public highway bridges. Roughly 51.2% are rated “Good,” 42.4% “Fair,” and 6.4% “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.
Good condition
51.2%
302 of 590 rated 7-9
Fair condition
42.4%
250 of 590 rated 5-6
Poor condition
6.4%
38 of 590 rated 4 or below
In-state Poor-share rank
#41 of 72
Among Wisconsin counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 590 NBI-tracked bridges by lowest applicable component rating.
Good 51.2% (302)
Fair 42.4% (250)
Poor 6.4% (38)
Dane County's Poor-condition bridges carry 317,362 vehicle crossings a day
That is 3.8% of the county's reported daily bridge traffic on 6.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 8,352 crossings a day against 12,521 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 590 of 590 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
32.7% of Dane County's bridges have passed the 50-year mark
193 of the 590 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 51.2% 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 13.6% of the county's Poor-condition bridge traffic
LRD JOHN NOLEN DR over LAKE MONONA, built 1975, carries 43,200 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 317,362 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Dane County's bridges were built
590 bridges with a recorded construction year, grouped by decade
- pre-1900 1
Built before 1900
1 bridges
- 1900s 2
1900–1909
2 bridges
- 1910s 1
1910–1919
1 bridges
- 1920s 6
1920–1929
6 bridges
- 1930s 17
1930–1939
17 bridges
- 1940s 8
1940–1949
8 bridges
- 1950s 45
1950–1959
45 bridges
- 1960s
1960–1969
99 bridges
- 1970s 33
1970–1979
33 bridges
- 1980s
1980–1989
49 bridges
- 1990s
1990–1999
122 bridges
- 2000s
2000–2009
68 bridges
- 2010s
2010–2019
99 bridges
- 2020s 40
2020–2029
40 bridges
What this shows Construction peaked in the 1990s, when 122 of the county's bridges still in the inventory were built, which is 20.7% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year (1987) matches the Wisconsin average (1984).
How Dane County compares with Wisconsin's closest counties by inventory size
The 5 Wisconsin counties nearest Dane County in number of bridges, with their condition splits. Its 6.4% Poor share is the 4th-lowest of these 6. Its average build year of 1987 against a peer-group mean of 1984 is in line with the group.
Showing the 5 closest of 71 Wisconsin counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Dane County (this page) | 590 | 51.2% | 42.4% | 6.4% | 1987 |
| Marathon County | 530 | 46.4% | 43.4% | 10.2% | 1982 |
| Brown County | 466 | 51.3% | 44.8% | 3.9% | 1990 |
| Grant County | 383 | 66.1% | 29.5% | 4.4% | 1984 |
| Monroe County | 374 | 50.5% | 46% | 3.5% | 1981 |
| Waukesha County | 369 | 53.1% | 40.4% | 6.5% | 1984 |
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 Dane 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 Dane County, both outside Wisconsin so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside WI (590 bridges here).
- Butler County, KS · 591 bridges
- Tulare County, CA · 589 bridges
- Knox County, TN · 588 bridges
- Comanche County, OK · 593 bridges
Similar average build year
Nearest mean year-built outside WI (1987 here).
- St. Louis County, MO · avg 1987 · 912 bridges
- Ellis County, TX · avg 1987 · 691 bridges
- St. Louis County, MN · avg 1987 · 663 bridges
- Palm Beach County, FL · avg 1987 · 610 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (302)
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.