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.

Total bridges

590

Public highway bridges in Dane County

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.

pre-1900

1
1900s

2
1910s

1
1920s

6
1930s

17
1940s

8
1950s

45
1960s

99
1970s

33
1980s

49
1990s

122
2000s

68
2010s

99
2020s

40

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.

Bridge inventory size and condition shares for Dane County and the 5 Wisconsin counties closest to it in inventory size
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.

All 590 Good 302 Fair 250 Poor 38

All bridges (590)

Sort:

Dane County Bridge Snapshot

Condition distribution

Dane County's Poor-condition bridges carry 317,362 vehicle crossings a day

32.7% of Dane County's bridges have passed the 50-year mark

One structure carries 13.6% of the county's Poor-condition bridge traffic

How Dane County compares with Wisconsin'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 (590)

IH 39 NB / IH 90 W

IH 39 SB / IH 90 E

IH I-39 NB/90 WB

CTH JG

IH 94 EB

IH 94 WB

CTH M

CTH F

LRD ELDER LANE NB

IH 39 SB / IH 90 E

CTH A

USH 18 EB-USH 151

USH 18 WB-USH 151

STH 92

STH 30 EB

STH 30 WB

CTH N

LRD SPOONER ST

USH 12 WB

LRD AIRPORT ROAD W

LRD SPRING ROSE RD

USH 51 NB

USH 51 SB

STH 19

LRD FERMITE DRIVE

CTH PB

IH 39 NB / IH 90 W

LRD WILLIAMSBURG W

CTH KP

LRD WILLIAMS DRIVE

CTH J

CTH F

IH 39 SB / IH 90 E

IH 39 NB / IH 90 W

USH 14

USH 18 WB-USH 151

USH 18 EB-USH 151

LRD NORTH SHORE BA

LRD EDGERTON ROAD

LRD RUTLEDGE ST

LRD E MAIN ST

CTH C/REINER ROAD

USH 12 EB

USH 12 WB

USH 12 EB

USH 12 WB

LRD RIVER RD

LRD SOUTH STREET

USH 18/151 VERONA

LRD GAMMON ROAD

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