FLAT IRON ROAD
Carrying FLAT IRON ROAD over MOKELER CREEK
0.4 MI. S. ILL 173, McHenry, Illinois
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: FLAT IRON ROAD
The FLAT IRON ROAD bridge in McHenry, Illinois carries FLAT IRON ROAD over MOKELER CREEK. It was built in 1950, making it 76 years old today. The structure is built primarily of concrete and spans 1 section, stretching 10.1 meters (33 feet) end to end. Daily traffic averages 1,550 vehicles, placing it in the moderately-trafficked tier of Illinois bridges. It is owned and maintained by County Highway Agency.
The latest FHWA inspection records show a deck rating of 4/9, 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 9.7 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How FLAT IRON ROAD 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 How the historical reference is calculated.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
- 1950
- Material
- Concrete
- Number of Spans
- 1
- Structure Length
- 10.1 m (33 ft)
- Deck Width
- 9.3 m (31 ft)
- Owner
- County Highway Agency
- Avg Daily Traffic
- 1,550 vehicles/day
- Structure Number
- 056301900000000
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • At 4/9, the deck (driving surface) is in poor shape, with advanced wear flagged for priority repair.
- • At 4/9, the superstructure (beams and supports above the deck) is in poor shape, with advanced wear flagged for priority repair.
- • At 6/9, the substructure (piers and abutments) shows fair condition, with minor wear flagged for upkeep.
How to read this record
FLAT IRON ROAD 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 FLAT IRON ROAD against other structures in McHenry 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 FLAT IRON ROAD?
FLAT IRON ROAD in McHenry, Illinois has a deck rating of 4/9, superstructure rating of 4/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is FLAT IRON ROAD inspected?
FLAT IRON ROAD'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 1,550 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. FLAT IRON ROAD 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 FLAT IRON ROAD?
FLAT IRON ROAD has an NBI inventory load rating of 9.7 metric tons.
Who is responsible for maintaining FLAT IRON ROAD?
FLAT IRON ROAD is owned and maintained by County Highway Agency.
How old is FLAT IRON ROAD and does age affect safety?
FLAT IRON ROAD was built in 1950, making it 76 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.