FOREST ROAD 421
Carrying FOREST ROAD 421 over MALLARD CREEK
NO DATA ENTERED, Idaho, Idaho
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: FOREST ROAD 421
The FOREST ROAD 421 bridge in Idaho, Idaho carries FOREST ROAD 421 over MALLARD CREEK. It was built in 1992, making it 34 years old today. The structure is built primarily of wood or timber and spans 1 section, stretching 9.9 meters (32 feet) end to end. Daily traffic averages 50 vehicles, placing it in the lower-traffic tier of Idaho bridges. It is owned and maintained by U.S. Forest Service.
The latest FHWA inspection records show a deck rating of 7/9, superstructure at 7/9, substructure at 6/9. The weakest component sits in fair condition. None of this bridge's reported major components fall into the Poor condition range. Its NBI inventory load rating is 17.5 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How FOREST ROAD 421 compares
Live comparison across Idaho.
Historical Sufficiency Rating
PlainBridge-computedFHWA discontinued this calculated item; it does not determine current condition, funding eligibility, posting, or closure. How the historical reference is calculated.
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Structural Details
- Year Built
- 1992
- Material
- Wood or Timber
- Number of Spans
- 1
- Structure Length
- 9.9 m (32 ft)
- Deck Width
- 4.9 m (16 ft)
- Owner
- U.S. Forest Service
- Avg Daily Traffic
- 50 vehicles/day
- Structure Number
- 011705000000079
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • The deck (driving surface) rates good at 7/9, with no significant deterioration on file.
- • At 7/9, the superstructure (beams and supports above the deck) is in good shape and shows no significant wear.
- • The substructure (piers and abutments) is in fair condition (6/9), with minor deterioration that may require routine maintenance.
How to read this record
This page shows what the last federal inspection recorded, not whether FOREST ROAD 421 is safe to cross today. Here is how to use it.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Learn how the 0–9 condition scale and Good/Fair/Poor categories are defined. How condition ratings work
- Compare FOREST ROAD 421 against other structures in Idaho and across Idaho. Idaho bridges
- Noticed visible damage or a safety concern? Report it to the agency that owns the bridge, or call 911 in an emergency. How to report a bridge
Condition codes come straight from the FHWA National Bridge Inventory and are not a real-time safety judgment. Only the owning agency, a state DOT, county, or other owner, can post, restrict, or close a bridge.
Frequently Asked Questions
What do the condition ratings mean for FOREST ROAD 421?
FOREST ROAD 421 in Idaho, Idaho has a deck rating of 7/9, superstructure rating of 7/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is FOREST ROAD 421 inspected?
FOREST ROAD 421's responsible agency sets its routine interval under FHWA's risk-based inspection rules; this page does not expose the scheduled interval. It carries about 50 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. FOREST ROAD 421 is currently shown as Fair condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for FOREST ROAD 421?
FOREST ROAD 421 has an NBI inventory load rating of 17.5 metric tons.
Who is responsible for maintaining FOREST ROAD 421?
FOREST ROAD 421 is owned and maintained by U.S. Forest Service.
How old is FOREST ROAD 421 and does age affect safety?
FOREST ROAD 421 was built in 1992, making it 34 years old.
Disclaimer: Bridge condition data is from the FHWA NBI and reflects the last reported inspection. A Poor condition rating is not a live declaration that a bridge is closed or unsafe for travel. For current closure, posting, or safety information, contact the responsible transportation agency.
Every figure on PlainBridge is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.