US Bridges

Is 55 S over Unknown RR

Fair

Jefferson County, Missouri · S 1916 T 40 N R 6 E · Structure no. 1902

Built
1969
56 years old
Condition
Fair
inspected November 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
186 ft
3 main spans
Daily traffic
16,629
2024 count
Owner
State
State Highway Agency

About this bridge

Is 55 S over Unknown RR is a steel continuous stringer/multi-beam or girder carrying Is 55 S over Unknown RR in Jefferson County, Missouri. It was built in 1969, so it is 56 years old, older than the Missouri average of 45.1 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 16,629 vehicles a day, roughly 22% of them trucks, projected to reach 30,764 by 2044. The structure is 186 ft (56.7 m) long and 41 ft wide. If it were closed, the detour would be 0.6 mi (1 km).

Location

Open in Google Maps
CarriesIs 55 S
CrossesUnknown RR
LocationS 1916 T 40 N R 6 E
RouteInterstate 55
CountyJefferson County
StateMissouri
Coordinates38.1851, -90.38866
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating66.5 US tons
Inventory rating39.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20 + Mod
Structure length186 ft (56.7 m)
Longest span73 ft (22.3 m)
Deck width41 ft (12.4 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic16,629 (2024)
Projected traffic30,764 by 2044
Trucks22%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesRailroad
Detour if closed0.6 mi (1 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 statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Is 55 S over Unknown RR built?

It was built in 1969, making it 56 years old in 2025.

What condition is Is 55 S over Unknown RR 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 November 2024.

How much traffic does Is 55 S over Unknown RR carry?

About 16,629 vehicles per day (2024 count), of which roughly 22% are trucks.

How long is Is 55 S over Unknown RR?

The structure is 186 ft (56.7 m) long with a longest span of 73 ft (22.3 m) and a deck 41 ft wide.

Who owns Is 55 S over Unknown RR?

It is owned by the State Highway Agency.