US HIGHWAY 12
Carrying US HIGHWAY 12 over LITTLE MISSOURI RIVER
AT MARMARTH, Slope, North Dakota
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
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. Its NBI inventory load rating is 37.7 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How US HIGHWAY 12 compares
Live comparison across North Dakota.
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 How the historical reference is calculated.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
- 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
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗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.
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.
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.