US Bridges

I-90 W-S Ramp over I-90 Mainline

Fair

King County, Washington · JCT I-405 · Structure no. 0008190E0000000

Built
1969
56 years old
Condition
Fair
inspected August 2023
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
464 ft
4 main spans
Daily traffic
15,468
2023 count
Owner
State
State Highway Agency

About this bridge

I-90 W-S Ramp over I-90 Mainline is a concrete continuous box beam or girders - multiple carrying I-90 W-S Ramp 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 15,468 vehicles a day, roughly 5% of them trucks, projected to reach 23,485 by 2039. The structure is 464 ft (141.4 m) long and 27 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-90 W-S Ramp
CrossesI-90 Mainline
LocationJCT I-405
RouteInterstate 90
CountyKing County
StateWashington
Coordinates47.58078, -122.17333
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 inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99 US tons
Inventory rating62.9 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length464 ft (141.4 m)
Longest span146 ft (44.5 m)
Deck width27 ft (8.1 m)
Roadway width23 ft (7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic15,468 (2023)
Projected traffic23,485 by 2039
Trucks5%
Lanes on structure1
Traffic directionOne-way traffic
CarriesOverpass structure at an interchange
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$5.5 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-90 W-S Ramp over I-90 Mainline built?

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

What condition is I-90 W-S Ramp 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 August 2023.

How much traffic does I-90 W-S Ramp over I-90 Mainline carry?

About 15,468 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is I-90 W-S Ramp over I-90 Mainline?

The structure is 464 ft (141.4 m) long with a longest span of 146 ft (44.5 m) and a deck 27 ft wide.

Who owns I-90 W-S Ramp over I-90 Mainline?

It is owned by the State Highway Agency.