ILL 15 & 4
Carrying ILL 15 & 4 over KASKASKIA RIVER
0.2 M E JCT ILL 4, St. Clair, Illinois
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: ILL 15 & 4
The ILL 15 & 4 bridge in St. Clair, Illinois carries ILL 15 & 4 over KASKASKIA RIVER. It was built in 1946, making it 80 years old today. It was last reconstructed in 2013, extending its service life. The structure is built primarily of steel and spans 1 section, stretching 278.1 meters (912 feet) end to end. Daily traffic averages 3,600 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 5/9, superstructure at 4/9, substructure at 7/9. The weakest component sits in poor condition. At least one major component here scores 4 or below, which produces a Poor condition classification under FHWA's current reporting rules. Its NBI inventory load rating is 32.1 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How ILL 15 & 4 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 How the historical reference is calculated.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
- 1946
- Last Reconstructed
- 2013
- Material
- Steel
- Number of Spans
- 1
- Structure Length
- 278.1 m (912 ft)
- Deck Width
- 10.4 m (34 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 3,600 vehicles/day
- Structure Number
- 082007700000000
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • The deck (driving surface) rates fair at 5/9, minor deterioration that routine maintenance should address.
- • The superstructure (beams and supports above the deck) rates poor at 4/9, advanced deterioration that should be prioritized for repair.
- • The substructure (piers and abutments) is in good condition (7/9), showing no significant deterioration.
How to read this record
ILL 15 & 4 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 ILL 15 & 4 against other structures in St. Clair 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 ILL 15 & 4?
ILL 15 & 4 in St. Clair, Illinois has a deck rating of 5/9, superstructure rating of 4/9, and substructure rating of 7/9 on the FHWA's 0–9 scale.
How often is ILL 15 & 4 inspected?
ILL 15 & 4'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 3,600 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. ILL 15 & 4 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 ILL 15 & 4?
ILL 15 & 4 has an NBI inventory load rating of 32.1 metric tons.
Who is responsible for maintaining ILL 15 & 4?
ILL 15 & 4 is owned and maintained by State Highway Agency.
How old is ILL 15 & 4 and does age affect safety?
ILL 15 & 4 was built in 1946, making it 80 years old and last reconstructed in 2013.
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.