County profile · official public datasets

Snohomish County, WA

500 public highway bridges tracked in the FHWA National Bridge Inventory: 49% rated Good, 47% Fair, 4% Poor.

500
Public bridges: 49%
Good condition: 4%
Poor condition

The verdict

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

Snohomish 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 28%
lowest Poor share in state: 4%
Poor-condition share: 500
public highway bridges: 1980
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.

Snohomish County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Snohomish County ranks #11 of 39 Washington counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4%). Snohomish County, Washington contains 500 public highway bridges. Roughly 49% are rated “Good,” 47% “Fair,” and 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

500

Public highway bridges in Snohomish County

Good condition

49%

245 of 500 rated 7-9

Fair condition

47%

235 of 500 rated 5-6

Poor condition

20 of 500 rated 4 or below

In-state Poor-share rank

#11 of 39

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

Condition distribution

Share of 500 NBI-tracked bridges by lowest applicable component rating.

Good

49% (245)

Fair

47% (235)

Poor

4% (20)

Snohomish County's Poor-condition bridges carry 152,948 vehicle crossings a day

That is 2% of the county's reported daily bridge traffic on 4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 7,647 crossings a day against 13,761 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 500 of 500 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

47.4% of Snohomish County's bridges have passed the 50-year mark

237 of the 500 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 49% 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 10.6% of the county's Poor-condition bridge traffic

SR 529 over STEAMBOAT SLOUGH, built 1927, carries 16,203 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 20-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 152,948 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

3
1920s

6
1930s

12
1940s

12
1950s

37
1960s

131
1970s

53
1980s

56
1990s

76
2000s

62
2010s

37
2020s

15

What this shows Construction peaked in the 1960s, when 131 of the county's bridges still in the inventory were built, which is 26.2% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1980, 5 years newer than the Washington average of 1975.

How Snohomish County compares with Washington's closest counties by inventory size

The 5 Washington counties nearest Snohomish County in number of bridges, with their condition splits. Its 4% Poor share is the 2nd-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1973 is 7 years newer.

Showing the 5 closest of 38 Washington counties eligible for comparison.

Bridge inventory size and condition shares for Snohomish County and the 5 Washington counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Yakima County	558	58.2%	36.7%	5%	1973
Snohomish County (this page)	500	49%	47%	4%	1980
Pierce County	472	55.3%	40.5%	4.2%	1974
Lewis County	419	39.4%	56.8%	3.8%	1969
Grays Harbor County	363	48.8%	41.9%	9.4%	1978
Whatcom County	354	44.1%	50.6%	5.4%	1970

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

Similar inventory size

Nearest county inventories outside WA (500 bridges here).

Cochise County, AZ · 501 bridges
Ventura County, CA · 501 bridges
Lake County, IN · 501 bridges
Garfield County, OK · 504 bridges

Similar average build year

Nearest mean year-built outside WA (1980 here).

Tulsa County, OK · avg 1980 · 1,135 bridges
Miami-Dade County, FL · avg 1980 · 1,057 bridges
Pulaski County, AR · avg 1980 · 721 bridges
McLennan County, TX · avg 1980 · 714 bridges

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

All 500 Good 245 Fair 235 Poor 20

Good-condition bridges (245)

Sort:

Snohomish County Bridge Snapshot

Condition distribution

Snohomish County's Poor-condition bridges carry 152,948 vehicle crossings a day

47.4% of Snohomish County's bridges have passed the 50-year mark

One structure carries 10.6% of the county's Poor-condition bridge traffic

How Snohomish County compares with Washington'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 (245)

I-5

I-5

153rd Street SE

SR 529

I-5

I-5

I-5

I-5

I-5

SR 527

N-E RAMP

MANN RD

I-5

I-5

SR 530

311 TH AVE SE

Smith Avenue

ROAD

I-5

I-5

ROAD

BEN HOWARD ROAD

180th St. SE

236TH ST SW

SR 522

OSO LOOP RD

75TH ST SE

I-5

ROAD

SWEDE HEAVEN RD

GIBSON RD.

342nd DR NE

SR 529

SR 529

I-5

GRANT CREEK RD

US 2

Mill Creek Road

ROAD

BUCK ISLAND ROAD

THREE LAKES RD

SO LK STEVENS RD

I-405

US 2 RAMP

BEAR CR RD

PIONEER HIGHWAY

SWEDE HEAVEN RD

N. BROOKS CR RD

SOUTH MACHIAS RD

Riverside Road

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