Thorne Bay Road over Rio Roberts
Prince of Wales-Hyder Census Area, Alaska · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Thorne Bay Road over Rio Roberts in Prince of Wales-Hyder Census Area, Alaska, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 6 (satisfactory condition) on the 0-9 scale.
- It was built in 1975, making it 50 years old at the 2025 inventory.
- It carries about 190 vehicles a day (traffic count year 2020).
- Its listed owner is the state highway agency.
- It is one of 79 of the 226 inventoried bridges in Prince of Wales-Hyder Census Area rated fair (35.0%); 16 (7.1%) 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 July 2023, on a 24-month routine inspection cycle.
- It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
- 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 → (55.69389, -132.77583)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 7 | 7 | Good condition |
| Superstructure | 6 | 6 | Satisfactory condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Continuous steel girder and floorbeam |
| Length | about 125 ft |
| Location | Mile Point 5.1 |
| NBI structure number | 1456 |
| 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) | 8: foundations stable, scour above the top of the footing |
| Fracture critical (item 92A) | Yes |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Alaska department of transportation.
Busiest bridges in Prince of Wales-Hyder Census Area
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Irr:craig/klwk Hwy over Klawock River | 1990 | 1,990 | Fair |
| Craig/klawock/holl over Crab Creek Culvert | 1985 | 1,200 | Poor |
| Big Salt Lake Road over Bennett Creek | 1985 | 680 | Good |
| Big Salt Lake Road over Steelhead River | 1998 | 400 | Good |
| Salmon River Road over Fish Creek | 1965 | 390 | Fair |
| N Prince of Wales over Yatuk Creek | 1990 | 340 | Good |
All bridges nearby: Prince of Wales-Hyder Census Area, AK bridge conditions · every bridge in Prince of Wales-Hyder Census Area · Alaska bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.