I-39 SB/US 51SB
Carrying I-39 SB/US 51SB over C & NW RR
0.21 MI N OF US 52, LaSalle, Illinois
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: I-39 SB/US 51SB
The I-39 SB/US 51SB bridge in LaSalle, Illinois carries I-39 SB/US 51SB over C & NW RR. It was built in 1977, making it 49 years old today. The structure is built primarily of prestressed concrete and spans 3 sections, stretching 53.6 meters (176 feet) end to end. Daily traffic averages 9,350 vehicles, placing it in the moderately-trafficked tier of Illinois bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection records show a deck rating of 6/9, superstructure at 4/9, substructure at 6/9. The weakest component sits in poor condition. A component scored 4 or below, placing this bridge in the federal Poor condition category rather than declaring it unsafe or closed. Its NBI inventory load rating is 30.8 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How I-39 SB/US 51SB compares
Live comparison across Illinois.
Historical Sufficiency Rating
PlainBridge-computedFHWA discontinued this calculated item; it does not determine current condition, funding eligibility, posting, or closure. How the historical reference is calculated.
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Structural Details
- Year Built
- 1977
- Material
- Prestressed Concrete
- Number of Spans
- 3
- Structure Length
- 53.6 m (176 ft)
- Deck Width
- 12.8 m (42 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 9,350 vehicles/day
- Structure Number
- 050016700000000
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • The deck (driving surface) rates fair at 6/9, minor deterioration that routine maintenance should address.
- • At 4/9, the superstructure (beams and supports above the deck) is in poor shape, with advanced wear flagged for priority repair.
- • The substructure (piers and abutments) rates fair at 6/9, minor deterioration that routine maintenance should address.
How to read this record
I-39 SB/US 51SB is in the federal Poor condition category. That is a component-based result, not a closure order.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Understand what Poor condition does and does not mean before drawing conclusions. Poor condition explained
- Compare I-39 SB/US 51SB against other structures in LaSalle and across Illinois. Illinois bridges
- Noticed visible damage or a safety concern? Report it to the agency that owns the bridge, or call 911 in an emergency. How to report a bridge
Condition codes come straight from the FHWA National Bridge Inventory and are not a real-time safety judgment. Only the owning agency, a state DOT, county, or other owner, can post, restrict, or close a bridge.
Frequently Asked Questions
What do the condition ratings mean for I-39 SB/US 51SB?
I-39 SB/US 51SB in LaSalle, Illinois has a deck rating of 6/9, superstructure rating of 4/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is I-39 SB/US 51SB inspected?
I-39 SB/US 51SB's responsible agency sets its routine interval under FHWA's risk-based inspection rules; this page does not expose the scheduled interval. It carries about 9,350 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. I-39 SB/US 51SB is currently shown as Poor condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for I-39 SB/US 51SB?
I-39 SB/US 51SB has an NBI inventory load rating of 30.8 metric tons.
Who is responsible for maintaining I-39 SB/US 51SB?
I-39 SB/US 51SB is owned and maintained by State Highway Agency.
How old is I-39 SB/US 51SB and does age affect safety?
I-39 SB/US 51SB was built in 1977, making it 49 years old.
Disclaimer: Bridge condition data is from the FHWA NBI and reflects the last reported inspection. A Poor condition rating is not a live declaration that a bridge is closed or unsafe for travel. For current closure, posting, or safety information, contact the responsible transportation agency.
Every figure on PlainBridge is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.