US101 (HWY 9)

US101 (HWY 9) carries traffic over Siuslaw River in Lane County, Oregon. Built in 1936, this structure is 90 years old, making it a historic structure that has served the community for generations. The bridge features steel construction with a movable - bascule design, a combination chosen by engineers to meet the specific requirements of this crossing.

Approximately 9,007 vehicles cross this bridge daily, indicating lower traffic volumes common for local roads and rural routes. While traffic is lighter, these bridges still serve essential community transportation needs. Commercial trucks account for 19% of all crossings. This heavy commercial usage significantly impacts structural wear, as a single fully-loaded truck can cause as much deck wear as thousands of passenger vehicles. Transportation planners factor this into maintenance scheduling and budget allocation.

The bridge is currently rated in poor condition based on federal inspection criteria established by the Federal Highway Administration. It is classified as structurally deficient, meaning one or more components have received a rating of 4 or below on the 0-9 scale. This designation indicates significant deterioration that warrants attention, though the bridge remains safe for travel within its posted limits. Structurally deficient does not mean unsafe—rather, it signals that repairs or replacement should be prioritized in transportation planning. With a total length of 165 feet, this structure falls within the typical range requiring standard inspection procedures conducted by certified bridge inspectors.

Steel bridges provide high strength-to-weight ratios, making them suitable for longer spans. However, they require ongoing protection against corrosion through painting or weathering steel designs. Inspectors pay close attention to connection points, fatigue cracking, and coating condition.

Federal law requires that all highway bridges be inspected at least every 24 months by qualified inspectors following the National Bridge Inspection Standards (NBIS). Some bridges with known issues or unusual characteristics may be inspected more frequently. Inspection data is reported to the National Bridge Inventory, a database maintained by the Federal Highway Administration that tracks the condition of all public highway bridges in the United States. This bridge data is sourced from that federal database and reflects the most recent available inspection results.