Structure 18031 · Custer County, ID
Carries US 93 over Salmon River;challis Br., 2.6 S. Challis.
Set by its lowest-rated component: Deck and Substructure at 7 of 9.
How ratings work306 ft end to end, longest span 150 ft: about 4 semi-trucks nose to tail. Lengths and the semi-truck on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a multi-beam bridge.
| State | Idaho |
| County | Custer |
| Location | 2.6 S. Challis |
| Carries | US 93 |
| Crosses | Salmon River;challis Br. |
| Coordinates | 44.47136, -114.20406 |
| Material | Steel Continuous |
| Design | Stringer/Multi-beam |
| Total Length | 306.1 ft (93.3 m) |
| Max Span | 149.9 ft (45.7 m) |
| Deck Width | 42.0 ft (12.8 m) |
| Deck Area | 1194.2 sq m |
| Main Spans | 2 |
| Year Built | 1995 |
| Avg Daily Traffic | 1,400 (2023) |
| Truck Traffic | 20% |
| Lanes On Bridge | 2 |
| Last Inspection | October 2024 |
| Inspection Frequency | Every 48 months |
| Owner | State Highway Agency |
| Historical Significance | Historical significance is not determined |
| Scour Critical | 8 — Stable, low risk |
| Structure Number | 000000000018031 |
Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."
A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.