Observatory Ave over US 218
Johnson County, Iowa · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Observatory Ave over US 218 in Johnson County, Iowa, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1980, making it 45 years old at the 2025 inventory.
- It carries about 1,580 vehicles a day (traffic count year 2022).
- Its listed owner is the state highway agency.
- It is one of 186 of the 376 inventoried bridges in Johnson County rated fair (49.5%); 34 (9.0%) 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 July 2023, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (41.55448, -91.54514)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 7 | 7 | Good condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Prestressed concrete stringer or multi-beam girder |
| Length | about 262 ft |
| Location | At Hills IA Interchange |
| NBI structure number | 000000000604605 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2023 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | N: not over a waterway |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Iowa department of transportation.
Busiest bridges in Johnson County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 80 EB over Iowa River | 1960 | 32,900 | Good |
| US 218 over Deer Creek | 1970 | 32,400 | Good |
| I 80 WB over Iowa River | 1960 | 32,050 | Good |
| EB I-80 over over US 6 & Iais RR | 1995 | 31,000 | Fair |
| I 80 WB over over US 6 & Iais RR | 1992 | 31,000 | Fair |
| EB I-80 over Cic Railway | 1963 | 30,600 | Fair |
All bridges nearby: Johnson County, IA bridge conditions · every bridge in Johnson County · Iowa bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.