US Bridges

SR 18 over Npry & City Streets

Fair

King County, Washington · 1.0 E JCT SR 167 · Structure no. 0005082A0000000

Built
1956
69 years old, rebuilt 1975
Condition
Fair
inspected July 2023
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
1,151 ft
16 main spans
Daily traffic
41,223
2023 count
Owner
State
State Highway Agency

About this bridge

SR 18 over Npry & City Streets is a concrete continuous box beam or girders - multiple carrying SR 18 over Npry & City Streets in King County, Washington. It was built in 1956 and reconstructed in 1975, so it is 69 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 41,223 vehicles a day, roughly 11% of them trucks, projected to reach 59,533 by 2039. The structure is 1,151 ft (350.8 m) long and 71 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesSR 18
CrossesNpry & City Streets
Location1.0 E JCT SR 167
RouteState Highway 18
CountyKing County
StateWashington
Coordinates47.30358, -122.23294
Functional classUrban Principal Arterial - Other Freeway or Expressway

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 inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating73 US tons
Inventory rating43 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans16
Design loadHS 20
Structure length1,151 ft (350.8 m)
Longest span96 ft (29.3 m)
Deck width71 ft (21.6 m)
Roadway width69 ft (21.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic41,223 (2023)
Projected traffic59,533 by 2039
Trucks11%
Lanes on structure5
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway and railroad
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 statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$41 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 18 over Npry & City Streets built?

It was built in 1956, making it 69 years old in 2025. It was reconstructed in 1975.

What condition is SR 18 over Npry & City Streets 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 2023.

How much traffic does SR 18 over Npry & City Streets carry?

About 41,223 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is SR 18 over Npry & City Streets?

The structure is 1,151 ft (350.8 m) long with a longest span of 96 ft (29.3 m) and a deck 71 ft wide.

Who owns SR 18 over Npry & City Streets?

It is owned by the State Highway Agency.