US Bridges

SR 509 over So 168th ST

Good

King County, Washington · 5.7 N JCT SR 516 · Structure no. 0011070B0000000

Built
1979
46 years old
Condition
Good
inspected August 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
171 ft
3 main spans
Daily traffic
14,997
2023 count
Owner
State
State Highway Agency

About this bridge

SR 509 over So 168th ST is a prestressed concrete continuous stringer/multi-beam or girder carrying SR 509 over So 168th ST in King County, Washington. It was built in 1979, so it is 46 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 14,997 vehicles a day, roughly 5% of them trucks, projected to reach 23,190 by 2039. The structure is 171 ft (52.1 m) long and 87 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

CarriesSR 509
CrossesSo 168th ST
Location5.7 N JCT SR 516
RouteState Highway 509
Coordinates47.45222, -122.32503
Functional classUrban Principal Arterial - Other Freeway or Expressway

Condition and inspection

Good

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
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 geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating77.9 US tons
Inventory rating47 US tons

Structure

MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length171 ft (52.1 m)
Longest span70 ft (21.3 m)
Deck width87 ft (26.4 m)
Roadway width82 ft (25 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic14,997 (2023)
Projected traffic23,190 by 2039
Trucks5%
Lanes on structure4
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed8.1 mi (13 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$7 million (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was SR 509 over So 168th ST built?

It was built in 1979, making it 46 years old in 2025.

What condition is SR 509 over So 168th ST 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 August 2023.

How much traffic does SR 509 over So 168th ST carry?

About 14,997 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is SR 509 over So 168th ST?

The structure is 171 ft (52.1 m) long with a longest span of 70 ft (21.3 m) and a deck 87 ft wide.

Who owns SR 509 over So 168th ST?

It is owned by the State Highway Agency.