County profile · official public datasets

Williamson County, TN

520 public highway bridges tracked in the FHWA National Bridge Inventory: 63.5% rated Good, 33.1% Fair, 3.5% Poor.

520
Public bridges: 63.5%
Good condition: 3.5%
Poor condition

The verdict

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

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

Top 46%
lowest Poor share in state: 3.5%
Poor-condition share: 520
public highway bridges: 1984
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.

Williamson County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Williamson County ranks #44 of 95 Tennessee counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3.5%). Williamson County, Tennessee contains 520 public highway bridges. Roughly 63.5% are rated “Good,” 33.1% “Fair,” and 3.5% “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

520

Public highway bridges in Williamson County

Good condition

63.5%

330 of 520 rated 7-9

Fair condition

33.1%

172 of 520 rated 5-6

Poor condition

3.5%

18 of 520 rated 4 or below

In-state Poor-share rank

#44 of 95

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

Condition distribution

Share of 520 NBI-tracked bridges by lowest applicable component rating.

Good

63.5% (330)

Fair

33.1% (172)

Poor

3.5% (18)

Williamson County's Poor-condition bridges carry 481,525 vehicle crossings a day

That is 8.2% of the county's reported daily bridge traffic on 3.5% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 26,751 crossings a day against 11,385 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 520 of 520 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

29.6% of Williamson County's bridges have passed the 50-year mark

154 of the 520 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 63.5% 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 22.8% of the county's Poor-condition bridge traffic

I65 over BRANCH, built 1963, carries 109,713 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 18-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 481,525 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

6
1930s

19
1940s

23
1950s

31
1960s

48
1970s

45
1980s

98
1990s

77
2000s

101
2010s

64
2020s

7

What this shows Construction peaked in the 2000s, when 101 of the county's bridges still in the inventory were built, which is 19.4% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1984, 7 years newer than the Tennessee average of 1977.

How Williamson County compares with Tennessee's closest counties by inventory size

The 5 Tennessee counties nearest Williamson County in number of bridges, with their condition splits. Its 3.5% Poor share is the 2nd-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1977 is 7 years newer.

Showing the 5 closest of 94 Tennessee counties eligible for comparison.

Bridge inventory size and condition shares for Williamson County and the 5 Tennessee counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Knox County	588	49.8%	48.6%	1.5%	1974
Williamson County (this page)	520	63.5%	33.1%	3.5%	1984
Hamilton County	464	46.8%	47%	6.3%	1976
Rutherford County	428	60.3%	35.5%	4.2%	1977
Maury County	424	22.9%	70.8%	6.4%	1975
Madison County	418	31.8%	64.1%	4.1%	1983

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

Similar inventory size

Nearest county inventories outside TN (520 bridges here).

Madison County, IL · 523 bridges
Rapides County, LA · 523 bridges
Kent County, MI · 523 bridges
Montgomery County, MD · 515 bridges

Similar average build year

Nearest mean year-built outside TN (1984 here).

Hennepin County, MN · avg 1984 · 936 bridges
Duval County, FL · avg 1984 · 831 bridges
El Paso County, CO · avg 1984 · 686 bridges
Bell County, TX · avg 1984 · 660 bridges

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

All 520 Good 330 Fair 172 Poor 18

Good-condition bridges (330)

Sort:

Williamson County Bridge Snapshot

Condition distribution

Williamson County's Poor-condition bridges carry 481,525 vehicle crossings a day

29.6% of Williamson County's bridges have passed the 50-year mark

One structure carries 22.8% of the county's Poor-condition bridge traffic

How Williamson County compares with Tennessee's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (330)

I840

I840

I840

I840

I840

I840

I840

I840

I840

I840

I840

I840

I840

I840

NATCHEZ TRACE PARK

NATCHEZ TRACE PARK

NATCHEZ TRACE PARK

NATCHEZ TRACE PARK

NATCHEZ TRACE PARK

FAS 253

NFA 1917

NFA 842 350386P

NFA A024

NFA A027

FAS 46

NFA A164

NFA 1921 (SA 9420)

I840

I840

PARKER BRANCH ROAD

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