US Bridges

I-90 Ramp to I-405 over I-90 Mainline

Fair

King County, Washington · JCT I-405 · Structure no. 0008190B0000000

Built
1969
56 years old
Condition
Fair
inspected April 2024
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
454 ft
4 main spans
Daily traffic
21,663
2023 count
Owner
State
State Highway Agency

About this bridge

I-90 Ramp to I-405 over I-90 Mainline is a concrete continuous box beam or girders - multiple carrying I-90 Ramp to I-405 over I-90 Mainline in King County, Washington. It was built in 1969, so it is 56 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 21,663 vehicles a day, roughly 5% of them trucks, projected to reach 33,211 by 2039. The structure is 454 ft (138.4 m) long and 36 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-90 Ramp to I-405
CrossesI-90 Mainline
LocationJCT I-405
RouteInterstate 90
CountyKing County
StateWashington
Coordinates47.57989, -122.17528
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 alignment6: Equal to present minimum criteria
Operating rating84 US tons
Inventory rating48.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length454 ft (138.4 m)
Longest span135 ft (41.1 m)
Deck width36 ft (11.1 m)
Roadway width33 ft (10.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic21,663 (2023)
Projected traffic33,211 by 2039
Trucks5%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

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$8 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-90 Ramp to I-405 over I-90 Mainline built?

It was built in 1969, making it 56 years old in 2025.

What condition is I-90 Ramp to I-405 over I-90 Mainline 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-90 Ramp to I-405 over I-90 Mainline carry?

About 21,663 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is I-90 Ramp to I-405 over I-90 Mainline?

The structure is 454 ft (138.4 m) long with a longest span of 135 ft (41.1 m) and a deck 36 ft wide.

Who owns I-90 Ramp to I-405 over I-90 Mainline?

It is owned by the State Highway Agency.