US HIGHWAY 12
Carrying US HIGHWAY 12 over LITTLE MISSOURI RIVER
AT MARMARTH, Slope, North Dakota
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
US HIGHWAY 12 in Slope, North Dakota sits above 68% of rated North Dakota bridges on inventory load rating (38 t), while its 1950 build year is earlier than 91% of Slope's recorded-year cohort (43 bridges).
US HIGHWAY 12 in Slope, North Dakota is rated Fair in the FHWA's 2024 National Bridge Inventory. Built in 1950, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 6. The lowest applicable rating sets the federal condition category, so this Fair 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 ND:0012006555
INTERSTATE-ERA · STEEL · LONG-SPAN-RUN · TIED-CTRL · LOCAL-ADT · STANDARD-LOAD · CAT-FAIR
- INTERSTATE-ERA 1950–1979
- STEEL Steel
- LONG-SPAN-RUN 5 spans
- TIED-CTRL Tied control
- LOCAL-ADT Local ADT
- STANDARD-LOAD Standard load
- CAT-FAIR Fair
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: US HIGHWAY 12
The US HIGHWAY 12 bridge in Slope, North Dakota carries US HIGHWAY 12 over LITTLE MISSOURI RIVER. It was built in 1950, making it 76 years old today. It was last reconstructed in 1987, extending its service life. The structure is built primarily of steel continuous and spans 5 sections, stretching 126.2 meters (414 feet) end to end. Daily traffic averages 580 vehicles, placing it in the lower-traffic tier of North Dakota bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection records show a deck rating of 6/9, superstructure at 7/9, substructure at 6/9. The weakest component sits in fair condition. No reported major component scores in the Poor range under the current federal condition thresholds.
How US HIGHWAY 12 compares
Age against the county: built in 1950, earlier than 39 of Slope's 43 bridges with a recorded construction year (91%), against a county median build year of 1988. Age is not a defect on its own, but it is the population from which future Poor ratings are drawn.
Live comparison across North Dakota bridges with a recorded inventory load rating (4,249 of 4,255 rated).
US HIGHWAY 12 vs every rated North Dakota bridge
Inventory load rating (metric tons), FHWA NBI, this state
38 Top 32% higher than 68% of 4,249 bridges
rated North Dakota 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.
Slope inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 43 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
- 1950
- Last Reconstructed
- 1987
- Material
- Steel Continuous
- Number of Spans
- 5
- Structure Length
- 126.2 m (414 ft)
- Deck Width
- 13.7 m (45 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 580 vehicles/day
- Structure Number
- 0012006555
Condition Analysis
- • At 6/9, the deck (driving surface) shows fair condition, with minor wear flagged for upkeep.
- • At 7/9, the superstructure (beams and supports above the deck) is in good shape and shows no significant wear.
- • At 6/9, the substructure (piers and abutments) shows fair condition, with minor wear flagged for upkeep.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
This page shows what the last federal inspection recorded, not whether US HIGHWAY 12 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 US HIGHWAY 12 against other structures in Slope and across North Dakota. North Dakota 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 US HIGHWAY 12?
US HIGHWAY 12 in Slope, North Dakota has a deck rating of 6/9, superstructure rating of 7/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is US HIGHWAY 12 inspected?
US HIGHWAY 12'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 580 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. US HIGHWAY 12 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 US HIGHWAY 12?
US HIGHWAY 12 has an NBI inventory load rating of 37.7 metric tons.
Who is responsible for maintaining US HIGHWAY 12?
US HIGHWAY 12 is owned and maintained by State Highway Agency.
How old is US HIGHWAY 12 and does age affect safety?
US HIGHWAY 12 was built in 1950, making it 76 years old and last reconstructed in 1987.
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.
Share this inspection record
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.