State Route 255 over Mad River Slough
GoodHumboldt County, California · 01-HUM-255-R5.13 · Structure no. 04 0257
- Built
- 1981
- 44 years old
- Condition
- Good
- inspected September 2023
- Type
- Stringer/Multi-beam or Girder
- Prestressed Concrete Continuous
- Length
- 497 ft
- 9 main spans
- Daily traffic
- 4,300
- 2010 count
- Owner
- State
- State Highway Agency
About this bridge
State Route 255 over Mad River Slough is a prestressed concrete continuous stringer/multi-beam or girder carrying State Route 255 over Mad River Slough in Humboldt County, California. It was built in 1981, so it is 44 years old, younger than the California average of 54.8 years.
The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
It carries about 4,300 vehicles a day, roughly 9% of them trucks, projected to reach 5,651 by 2045. The structure is 497 ft (151.6 m) long and 43 ft wide. If it were closed, the detour would be 11.8 mi (19 km).
Location
Open in Google MapsCondition and inspection
All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 7 Good | Some minor problems. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 7 Good | Some minor problems. |
| Channel and channel protection | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was State Route 255 over Mad River Slough built?
It was built in 1981, making it 44 years old in 2025.
What condition is State Route 255 over Mad River Slough in?
The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in September 2023.
How much traffic does State Route 255 over Mad River Slough carry?
About 4,300 vehicles per day (2010 count), of which roughly 9% are trucks.
How long is State Route 255 over Mad River Slough?
The structure is 497 ft (151.6 m) long with a longest span of 55 ft (16.8 m) and a deck 43 ft wide.
Who owns State Route 255 over Mad River Slough?
It is owned by the State Highway Agency.