FOREST ROAD 421
Carrying FOREST ROAD 421 over LITTLE MALLARD CREEK
AT SALMON RIVER, Idaho, Idaho
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
FOREST ROAD 421 in Idaho, Idaho sits above 5% of rated Idaho bridges on inventory load rating (15 t), while its 1984 build year is earlier than 31% of Idaho's recorded-year cohort (215 bridges).
FOREST ROAD 421 in Idaho, Idaho is rated Poor in the FHWA's 2024 National Bridge Inventory. Built in 1984, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 2. The lowest applicable rating sets the federal condition category, so this Poor result describes the weakest reported component rather than the structure as a whole. No NBI category is a closure decision or a live crossing-safety verdict.
NBI record plate
Structure ID:011705000000082
LATE-CENTURY · TIMBER · SINGLE-SPAN · DECK-LED · LOCAL-ADT · LIGHT-LOAD · CAT-POOR
- LATE-CENTURY 1980–1999
- TIMBER Wood or timber
- SINGLE-SPAN Single span
- DECK-LED Deck-led
- LOCAL-ADT Local ADT
- LIGHT-LOAD Light load
- CAT-POOR Poor
Inspection-sheet codes from this record’s year, material family, spans, controlling component, ADT, inventory load, and NBI category, not a live closure verdict.
Bridge Snapshot: FOREST ROAD 421
The FOREST ROAD 421 bridge in Idaho, Idaho carries FOREST ROAD 421 over LITTLE MALLARD CREEK. It was built in 1984, making it 42 years old today. The structure is built primarily of wood or timber and spans 1 section, stretching 7.3 meters (24 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 2/9, superstructure at 5/9, substructure at 5/9. The weakest component sits in critical condition. At least one major component here scores 4 or below, which produces a Poor condition classification under FHWA's current reporting rules.
How FOREST ROAD 421 compares
Age against the county: built in 1984, earlier than 67 of Idaho's 215 bridges with a recorded construction year (31%), against a county median build year of 1968. This is one of the newer structures in its county.
Live comparison across Idaho bridges with a recorded inventory load rating (4,574 of 4,616 rated).
FOREST ROAD 421 vs every rated Idaho bridge
Inventory load rating (metric tons), FHWA NBI, this state
15 Top 95% higher than 5% of 4,574 bridges
rated Idaho bridges, bucketed by value
Each bar is a band; taller bars hold more bridges. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source FHWA National Bridge Inventory · August 2026
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Reported 0–9 component ratings from the FHWA NBI. The highlighted component is the lowest reported input to this record’s current condition category; it is not a closure or live crossing-safety decision.
Idaho inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 215 bridges in this county. Orthogonal to this structure's component profile above: a county catalog share, not a live crossing-safety verdict.
Structural Details
- Year Built
- 1984
- Material
- Wood or Timber
- Number of Spans
- 1
- Structure Length
- 7.3 m (24 ft)
- Deck Width
- 4.9 m (16 ft)
- Owner
- U.S. Forest Service
- Avg Daily Traffic
- 50 vehicles/day
- Structure Number
- 011705000000082
Condition Analysis
- • The deck (driving surface) is in critical condition (2/9), with severe deterioration recorded on the inspecting agency's 0-9 scale.
- • The superstructure (beams and supports above the deck) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
- • The substructure (piers and abutments) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
FOREST ROAD 421 is in the federal Poor condition category. That is a component-based result, not a closure order.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Understand what Poor condition does and does not mean before drawing conclusions. Poor condition explained
- 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 2/9, superstructure rating of 5/9, and substructure rating of 5/9 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 Poor 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 14.6 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 1984, making it 42 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.
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Send this source-bounded record or download its data card. An NBI condition category is not a closure or live crossing-safety verdict.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. Component ratings, ADT, and condition category on this page are copied from the NBI record for this structure; no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2024 NBI release. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.