US Bridges

SB I-405 Ramp over Benson Road

Good

King County, Washington · 0.4 N JCT SR 515 · Structure no. 0017624B0000000

Built
2010
15 years old
Condition
Good
inspected April 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
252 ft
2 main spans
Daily traffic
11,338
2022 count
Owner
State
State Highway Agency

About this bridge

SB I-405 Ramp over Benson Road is a prestressed concrete continuous stringer/multi-beam or girder carrying SB I-405 Ramp over Benson Road in King County, Washington. It was built in 2010, so it is 15 years old, younger than the Washington average of 49.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 11,338 vehicles a day, roughly 5% of them trucks, projected to reach 16,579 by 2039. The structure is 252 ft (76.8 m) long and 30 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesSB I-405 Ramp
CrossesBenson Road
Location0.4 N JCT SR 515
RouteInterstate 405
CountyKing County
StateWashington
Coordinates47.47367, -122.20422
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure7 GoodSome minor problems.
Substructure8 Very GoodNo problems noted.
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 rating89.9 US tons
Inventory rating54 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHL 93
Structure length252 ft (76.8 m)
Longest span123 ft (37.5 m)
Deck width30 ft (9 m)
Roadway width27 ft (8.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic11,338 (2022)
Projected traffic16,579 by 2039
Trucks5%
Lanes on structure1
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemYes

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$3.5 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SB I-405 Ramp over Benson Road built?

It was built in 2010, making it 15 years old in 2025.

What condition is SB I-405 Ramp over Benson Road in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in April 2024.

How much traffic does SB I-405 Ramp over Benson Road carry?

About 11,338 vehicles per day (2022 count), of which roughly 5% are trucks.

How long is SB I-405 Ramp over Benson Road?

The structure is 252 ft (76.8 m) long with a longest span of 123 ft (37.5 m) and a deck 30 ft wide.

Who owns SB I-405 Ramp over Benson Road?

It is owned by the State Highway Agency.