US Bridges

SR 18 W-S Ramp over I-5 & SR 18

Fair

King County, Washington · JCT I-5 · Structure no. 0017936B0000000

Built
2012
13 years old
Condition
Fair
inspected July 2024
Type
Box Beam or Girders - Single or Spread
Steel Continuous
Length
2,407 ft
5 main spans
Daily traffic
28,117
2023 count
Owner
State
State Highway Agency

About this bridge

SR 18 W-S Ramp over I-5 & SR 18 is a steel continuous box beam or girders - single or spread carrying SR 18 W-S Ramp over I-5 & SR 18 in King County, Washington. It was built in 2012, so it is 13 years old, younger 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 28,117 vehicles a day, roughly 12% of them trucks, projected to reach 41,111 by 2039. The structure is 2,407 ft (733.7 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesSR 18 W-S Ramp
CrossesI-5 & SR 18
LocationJCT I-5
RouteState Highway 18
CountyKing County
StateWashington
Coordinates47.28983, -122.30336
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.
Substructure8 Very GoodNo problems noted.
Last inspectionJuly 2024
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 rating43.2 US tons
Inventory rating31.4 US tons

Structure

Structure typeBox Beam or Girders - Single or Spread
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans5 (+9 approach)
Design loadHL 93
Structure length2,407 ft (733.7 m)
Longest span250 ft (76.2 m)
Deck width43 ft (13 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic28,117 (2023)
Projected traffic41,111 by 2039
Trucks12%
Lanes on structure2
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 statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$48 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 18 W-S Ramp over I-5 & SR 18 built?

It was built in 2012, making it 13 years old in 2025.

What condition is SR 18 W-S Ramp over I-5 & SR 18 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 July 2024.

How much traffic does SR 18 W-S Ramp over I-5 & SR 18 carry?

About 28,117 vehicles per day (2023 count), of which roughly 12% are trucks.

How long is SR 18 W-S Ramp over I-5 & SR 18?

The structure is 2,407 ft (733.7 m) long with a longest span of 250 ft (76.2 m) and a deck 43 ft wide.

Who owns SR 18 W-S Ramp over I-5 & SR 18?

It is owned by the State Highway Agency.