US Bridges

I-405 over SR 181

Fair

King County, Washington · 1.0 N JCT I-5 · Structure no. 0007249D0000000

Built
1964
61 years old, rebuilt 1987
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
173 ft
4 main spans
Daily traffic
77,251
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over SR 181 is a prestressed concrete stringer/multi-beam or girder carrying I-405 over SR 181 in King County, Washington. It was built in 1964 and reconstructed in 1987, so it is 61 years old, older than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 77,251 vehicles a day, roughly 6% of them trucks, projected to reach 112,423 by 2039. The structure is 173 ft (52.7 m) long and 169 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

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CarriesI-405
CrossesSR 181
Location1.0 N JCT I-5
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.46369, -122.24594
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating60 US tons
Inventory rating34.9 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length173 ft (52.7 m)
Longest span46 ft (14.1 m)
Deck width169 ft (51.6 m)
Roadway width154 ft (46.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic77,251 (2023)
Projected traffic112,423 by 2039
Trucks6%
Lanes on structure10
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed5 mi (8 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$12.5 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over SR 181 built?

It was built in 1964, making it 61 years old in 2025. It was reconstructed in 1987.

What condition is I-405 over SR 181 in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2024.

How much traffic does I-405 over SR 181 carry?

About 77,251 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over SR 181?

The structure is 173 ft (52.7 m) long with a longest span of 46 ft (14.1 m) and a deck 169 ft wide.

Who owns I-405 over SR 181?

It is owned by the State Highway Agency.