US Bridges

I-405 over Sunset Blvd (old SR 900)

Fair

King County, Washington · 0.5 N JCT SR 169 · Structure no. 0006912B0000000

Built
1963
62 years old, rebuilt 1994
Condition
Fair
inspected June 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
290 ft
4 main spans
Daily traffic
68,154
2023 count
Owner
State
State Highway Agency

About this bridge

I-405 over Sunset Blvd (old SR 900) is a prestressed concrete stringer/multi-beam or girder carrying I-405 over Sunset Blvd (old SR 900) in King County, Washington. It was built in 1963 and reconstructed in 1994, so it is 62 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 68,154 vehicles a day, roughly 6% of them trucks, projected to reach 99,185 by 2039. The structure is 290 ft (88.4 m) long and 110 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-405
CrossesSunset Blvd (old SR 900)
Location0.5 N JCT SR 169
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.49006, -122.19247
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating79 US tons
Inventory rating47 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length290 ft (88.4 m)
Longest span80 ft (24.4 m)
Deck width110 ft (33.5 m)
Roadway width106 ft (32.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic68,154 (2023)
Projected traffic99,185 by 2039
Trucks6%
Lanes on structure6
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 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 statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$14.9 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-405 over Sunset Blvd (old SR 900) built?

It was built in 1963, making it 62 years old in 2025. It was reconstructed in 1994.

What condition is I-405 over Sunset Blvd (old SR 900) 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 June 2023.

How much traffic does I-405 over Sunset Blvd (old SR 900) carry?

About 68,154 vehicles per day (2023 count), of which roughly 6% are trucks.

How long is I-405 over Sunset Blvd (old SR 900)?

The structure is 290 ft (88.4 m) long with a longest span of 80 ft (24.4 m) and a deck 110 ft wide.

Who owns I-405 over Sunset Blvd (old SR 900)?

It is owned by the State Highway Agency.