IL 171 SB
Carrying IL 171 SB over JOLIET RD&BN RR SPUR
0.5 M NW I-55, Cook, Illinois
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
IL 171 SB in Cook, Illinois sits above 18% of rated Illinois bridges on inventory load rating (28 t), while its 1964 build year is earlier than 44% of Cook's recorded-year cohort (1,721 bridges).
IL 171 SB in Cook, Illinois is rated Poor in the FHWA's 2024 National Bridge Inventory. Built in 1964, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 3. The lowest applicable rating sets the federal condition category, so this Poor result describes the weakest reported component rather than the structure as a whole. No NBI category is a closure decision or a live crossing-safety verdict.
NBI record plate
Structure IL:016100500000000
INTERSTATE-ERA · STEEL · LONG-SPAN-RUN · SUPER-LED · HEAVY-ADT · STANDARD-LOAD · CAT-POOR
- INTERSTATE-ERA 1950–1979
- STEEL Steel
- LONG-SPAN-RUN 6 spans
- SUPER-LED Superstructure-led
- HEAVY-ADT Heavy ADT
- STANDARD-LOAD Standard load
- CAT-POOR Poor
Inspection-sheet codes from this record’s year, material family, spans, controlling component, ADT, inventory load, and NBI category, not a live closure verdict.
Bridge Snapshot: IL 171 SB
The IL 171 SB bridge in Cook, Illinois carries IL 171 SB over JOLIET RD&BN RR SPUR. It was built in 1964, making it 62 years old today. It was last reconstructed in 1994, extending its service life. The structure is built primarily of steel and spans 6 sections, stretching 123.5 meters (405 feet) end to end. Daily traffic averages 40,100 vehicles, placing it in the heavily-trafficked tier of Illinois bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection records show a deck rating of 7/9, superstructure at 3/9, substructure at 7/9. The weakest component sits in poor condition. Because at least one major component scores 4 or lower, this bridge falls in FHWA's Poor condition category. That category is not a closure order.
How IL 171 SB compares
Age against the county: built in 1964, earlier than 755 of Cook's 1,721 bridges with a recorded construction year (44%), against a county median build year of 1962. This is one of the newer structures in its county.
Live comparison across Illinois bridges with a recorded inventory load rating (26,904 of 26,928 rated).
IL 171 SB vs every rated Illinois bridge
Inventory load rating (metric tons), FHWA NBI, this state
28 Top 82% higher than 18% of 26,904 bridges
rated Illinois bridges, bucketed by value
Each bar is a band; taller bars hold more bridges. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source FHWA National Bridge Inventory · August 2026
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Reported 0–9 component ratings from the FHWA NBI. The highlighted component is the lowest reported input to this record’s current condition category; it is not a closure or live crossing-safety decision.
Cook inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 1,721 bridges in this county. Orthogonal to this structure's component profile above: a county catalog share, not a live crossing-safety verdict.
Structural Details
- Year Built
- 1964
- Last Reconstructed
- 1994
- Material
- Steel
- Number of Spans
- 6
- Structure Length
- 123.5 m (405 ft)
- Deck Width
- 11.9 m (39 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 40,100 vehicles/day
- Structure Number
- 016100500000000
Condition Analysis
- • The deck (driving surface) rates good at 7/9, with no significant deterioration on file.
- • The superstructure (beams and supports above the deck) is in poor condition (3/9), showing advanced deterioration on the inspecting agency's 0-9 scale.
- • The substructure (piers and abutments) rates good at 7/9, with no significant deterioration on file.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
IL 171 SB 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 IL 171 SB against other structures in Cook 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 IL 171 SB?
IL 171 SB in Cook, Illinois has a deck rating of 7/9, superstructure rating of 3/9, and substructure rating of 7/9 on the FHWA's 0–9 scale.
How often is IL 171 SB inspected?
IL 171 SB'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 40,100 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. IL 171 SB 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 IL 171 SB?
IL 171 SB has an NBI inventory load rating of 28.2 metric tons.
Who is responsible for maintaining IL 171 SB?
IL 171 SB is owned and maintained by State Highway Agency.
How old is IL 171 SB and does age affect safety?
IL 171 SB was built in 1964, making it 62 years old and last reconstructed in 1994.
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.
Share this inspection record
Send this source-bounded record or download its data card. An NBI condition category is not a closure or live crossing-safety verdict.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. Component ratings, ADT, and condition category on this page are copied from the NBI record for this structure; no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2024 NBI release. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.