State Route 299 over Mad River
Humboldt County, California · rated Poor in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- State Route 299 over Mad River in Humboldt County, California, is rated in poor condition in the 2025 National Bridge Inventory (as of ).
- It was built in 1965, making it 60 years old at the 2025 inventory.
- It carries about 4,775 vehicles a day (traffic count year 2010).
- Its listed owner is the state highway agency.
- A poor rating means at least one major component - deck, superstructure, or substructure - is rated 4 or lower on FHWA's 0-9 scale. It does not by itself mean the bridge is unsafe; bridges judged unsafe are closed or load-restricted by their owners.
View this bridge on a map → (40.91034, -124.06274)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Deck | 4 | Poor condition |
| Superstructure | 7 | Good condition |
| Substructure | 7 | Good condition |
Bridge details
| Structure | Continuous steel stringer or multi-beam girder |
| Length | about 518 ft |
| Location | 01-hum-299-r1.56 |
| NBI structure number | 04 0036L |
Source: FHWA National Bridge Inventory, 2025 data as reported by the California department of transportation.
All bridges nearby: Humboldt County, CA bridge conditions · California bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.