County profile · official public datasets

King County, WA

1,238 public highway bridges tracked in the FHWA National Bridge Inventory: 46.5% rated Good, 49.2% Fair, 4.3% Poor.

1,238
Public bridges
46.5%
Good condition
4.3%
Poor condition

The verdict

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

King County posts a better-than-median Poor-condition share among rated counties in the state across large county bridge inventory.

Top 38%
lowest Poor share in state
4.3%
Poor-condition share
1,238
public highway bridges
1977
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.

King County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, King County ranks #15 of 39 Washington counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4.3%). King County, Washington contains 1,238 public highway bridges. Roughly 46.5% are rated “Good,” 49.2% “Fair,” and 4.3% “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

1,238

Public highway bridges in King County

Good condition

46.5%

576 of 1,238 rated 7-9

Fair condition

49.2%

609 of 1,238 rated 5-6

Poor condition

4.3%

53 of 1,238 rated 4 or below

In-state Poor-share rank

#15 of 39

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

Condition distribution

Share of 1,238 NBI-tracked bridges by lowest applicable component rating.

Good
46.5% (576)
Fair
49.2% (609)
Poor
4.3% (53)

King County's Poor-condition bridges carry 905,838 vehicle crossings a day

That is 3.2% of the county's reported daily bridge traffic on 4.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 17,420 crossings a day against 19,020 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 1,235 of 1,238 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

53.6% of King County's bridges have passed the 50-year mark

664 of the 1,238 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 46.5% 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 10.5% of the county's Poor-condition bridge traffic

I-5 over LUCILE ST, built 1966, carries 95,134 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 53-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 905,838 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When King County's bridges were built

1,238 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1960s, when 317 of the county's bridges still in the inventory were built, which is 25.6% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the Washington average (1975).

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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

The 5 Washington counties nearest King County in number of bridges, with their condition splits. Its 4.3% Poor share is the 4th-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1975 is in line with the group.

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

Bridge inventory size and condition shares for King County and the 5 Washington counties closest to it in inventory size
County Bridges Poor
King County (this page) 1,238 4.3%
Yakima County 558 5%
Snohomish County 500 4%
Pierce County 472 4.2%
Lewis County 419 3.8%
Grays Harbor County 363 9.4%

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

Similar inventory size

Nearest county inventories outside WA (1,238 bridges here).

Similar average build year

Nearest mean year-built outside WA (1977 here).

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

All 1,238 Good 576 Fair 609 Poor 53

Good-condition bridges (576)

I-90

Good

Over: GAME CROSSING

3.1 E JCT SR 18, King, WA

Built 1976 Load: 72.6 t ADT: 25,826

I-90

Good

Over: GAME CROSSING

3.1 E JCT SR 18, King, WA

Built 1976 Load: 72.6 t ADT: 25,826

SR 18

Good

Over: 244TH AVE SE

1.2 E JCT SR 169, King, WA

Built 2005 Load: 74.4 t ADT: 16,302

I-405 RAMP

Good

Over: SOUTHCENTER BLVD

0.9 N JCT I-5, King, WA

Built 1994 Load: 75.3 t ADT: 7,007

RAMP

Good

Over: E ISSAQUAH CREEK

2.1 E JCT SR 900, King, WA

Built 2003 Load: 75.3 t ADT: 2,230

I-90

Good

Over: CITY STREETS

0.2 W JCT I-5, King, WA

Built 1991 Load: 76.2 t ADT: 10,912

SR 202

Good

Over: LITTLE BEAR CREEK

0.1 E JCT SR 522, King, WA

Built 2017 Load: 76.5 t ADT: 39,506

NW WOODBINE WAY

Good

Over: TRAIL - MARY AVE NW

1500 NW WOODBINE WAY, King, WA

Built 1928 Load: 76.8 t ADT: 1,000

SR 99

Good

Over: DETENTION VAULT

0.9 N JCT SR 509, King, WA

Built 2010 Load: 78.9 t ADT: 38,696

EASTLAKE AVE

Good

Over: I-5 RAMPS

2.4 N JCT I-90, King, WA

Built 1963 Load: 79.7 t ADT: 14,621

N-E RAMP

Good

Over: 4TH AVE S

0.2 W JCT I-90, King, WA

Built 2003 Load: 79.8 t ADT: 7,545

SR 523 / NE 145TH

Good

Over: I-5

0.9 E JCT SR 99, King, WA

Built 1964 Load: 80.7 t ADT: 26,131

NW SAMMAMISH ROAD

Good

Over: TRIBUTARY 170

0.5 M WEST OF SR-900, King, WA

Built 2008 Load: 80.7 t ADT: 13,500

SR 520

Good

Over: PKWY & SAMMAMISH RIVER

4.9 E JCT I-405, King, WA

Built 1995 Load: 84.4 t ADT: 40,791

SW NEVADA ST

Good

Over: LONGFELLOW CREEK

SW Nevada St & 28th Ave, King, WA

Built 1988 Load: 84.4 t ADT: 400

NE 8TH STREET

Good

Over: KELSEY CREEK

0.01 E JCT 132ND AVE NE, King, WA

Built 2018 Load: 85.9 t ADT: 21,950

COVINGTON WAY SE

Good

Over: SR 18

7.1 E JCT SR 164, King, WA

Built 1997 Load: 86.2 t ADT: 4,000

15TH ST SW

Good

Over: SR 167

2.3 N PIERCE CO, King, WA

Built 1975 Load: 89.8 t ADT: 25,000

SR 516

Good

Over: GREEN RIVER

2.3 E JCT I-5, King, WA

Built 1984 Load: 89.8 t ADT: 23,306

CITY ST - 76TH AVE

Good

Over: I-90

4.0 E JCT I-5, King, WA

Built 1989 Load: 89.8 t ADT: 12,230

ISLAND CREST WAY

Good

Over: I-90

4.0 E JCT SR 900, King, WA

Built 1989 Load: 89.8 t ADT: 9,063

SR 202

Good

Over: MEADOWBROOK SLOUGH

5.8 E JCT SR 203, King, WA

Built 1995 Load: 89.8 t ADT: 11,250

W-W RAMP/3RD ST

Good

Over: C ST SW

1.0 E JCT SR 167, King, WA

Built 2002 Load: 89.8 t ADT: 9,187

SMITHERS AVE S

Good

Over: WETLAND

3.0 MI E OF SR 167, King, WA

Built 2017 Load: 96.9 t ADT: 75

Main ST

Good

Over: Stormwater Facility

0.01 W JCT 151 PL, King, WA

Built 2021 Load: 96.9 t ADT: 13,683

SAYBROOK DRIVE

Good

Over: BEAR CREEK

0.1 MI S JCT NE W-DUVALL, King, WA

Built 1992 Load: 96.9 t ADT: 3,000

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.