US Bridges

I-39 Sb/Us 51SB over C & NW RR

Poor

LaSalle County, Illinois · 0.21 MI N of US 52 · Structure no. 050016700000000

Built
1977
48 years old
Condition
Poor
inspected January 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
176 ft
3 main spans
Daily traffic
9,350
2023 count
Owner
State
State Highway Agency

About this bridge

I-39 Sb/Us 51SB over C & NW RR is a prestressed concrete stringer/multi-beam or girder carrying I-39 Sb/Us 51SB over C & NW RR in LaSalle County, Illinois. It was built in 1977, so it is 48 years old, older than the Illinois average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 9,350 vehicles a day, roughly 39% of them trucks, projected to reach 9,992 by 2046. The structure is 176 ft (53.6 m) long and 42 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-39 Sb/Us 51SB
CrossesC & NW RR
Location0.21 MI N of US 52
RouteInterstate 39
CountyLaSalle County
StateIllinois
Coordinates41.47649, -89.04952
Functional classRural Principal Arterial - Interstate

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJanuary 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44.3 US tons
Inventory rating34 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length176 ft (53.6 m)
Longest span60 ft (18.3 m)
Deck width42 ft (12.8 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,350 (2023)
Projected traffic9,992 by 2046
Trucks39%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesRailroad
Detour if closed1.2 mi (2 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 I-39 Sb/Us 51SB over C & NW RR built?

It was built in 1977, making it 48 years old in 2025.

What condition is I-39 Sb/Us 51SB over C & NW RR in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in January 2024.

How much traffic does I-39 Sb/Us 51SB over C & NW RR carry?

About 9,350 vehicles per day (2023 count), of which roughly 39% are trucks.

How long is I-39 Sb/Us 51SB over C & NW RR?

The structure is 176 ft (53.6 m) long with a longest span of 60 ft (18.3 m) and a deck 42 ft wide.

Who owns I-39 Sb/Us 51SB over C & NW RR?

It is owned by the State Highway Agency.