Il 173 over Piscasaw Creektrib.
Boone County, Illinois · rated Good in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Il 173 over Piscasaw Creektrib. in Boone County, Illinois, is rated in good condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the deck, rated 7 (good condition) on the 0-9 scale.
- It was built in 2001, making it 24 years old at the 2025 inventory.
- It carries about 5,000 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 45 of the 109 inventoried bridges in Boone County rated good (41.3%); 11 (10.1%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated April 2022, on a 48-month routine inspection cycle.
- A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.
View this bridge on a map → (42.40069, -88.70622)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 7 | 7 | Good condition |
Bridge details
| Structure | Continuous concrete slab |
| Length | about 89 ft |
| Location | at Mchenry Co. Ln. |
| NBI structure number | 004001800000000 |
| Condition class | Good |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | April 2022 |
| Inspection interval (item 91) | 48 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Illinois department of transportation.
Busiest bridges in Boone County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 90 over Stream | 2014 | 51,100 | Fair |
| I-90 over Stream | 1958 | 28,000 | Good |
| I 90 WB over Mosquito Crk | 2013 | 28,000 | Fair |
| I 90 EB over Mosquito Ckr | 2013 | 28,000 | Good |
| I-90 over Stream | 1958 | 25,700 | Fair |
| I-90 over Stream | 1958 | 25,550 | Good |
All bridges nearby: Boone County, IL bridge conditions · every bridge in Boone County · Illinois bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.