A50 (BRIDGE ST)
Carrying A50 (BRIDGE ST) over BIG SIOUX RIVER
098492519, Lyon, Iowa
FHWA NBI inspection record for this structure. Condition ratings, inventory load rating, span, deck width, and average daily traffic refresh annually with each NBI release.
Bridge Snapshot: A50 (BRIDGE ST)
The A50 (BRIDGE ST) bridge in Lyon, Iowa carries A50 (BRIDGE ST) over BIG SIOUX RIVER. It was built in 1971, making it 55 years old today. The structure is built primarily of steel continuous and spans 4 sections, stretching 106.1 meters (348 feet) end to end. Daily traffic averages 888 vehicles, placing it in the lower-traffic tier of Iowa bridges. It is owned and maintained by County Highway Agency, the entity responsible for routine inspections and any needed repairs.
The latest FHWA inspection records show a deck rating of 5/9, superstructure at 7/9, substructure at 5/9 on the 0–9 NBI scale, where 9 is excellent and 0 is failed. The weakest component sits in fair condition, which drives the overall status of this bridge. No major component scores in the poor range, so the bridge is not classified as structurally deficient under federal criteria. Its NBI inventory load rating is 29.2 metric tons — the load level the structure is rated to carry at inventory (long-term) level.
In a county that maintains hundreds of NBI-tracked bridges, A50 (BRIDGE ST) is one data point in a Iowa inventory that FHWA inspects on a two-year cycle (more often when ratings fall). Bridge age alone is not a reliable safety signal — a 55-era structure can outperform a newer one when maintenance is consistent, materials are sound, and traffic loads stay within design limits. Use the condition ratings above, the sufficiency score, and the structurally-deficient flag together to read the bridge's real status, and check the linked county and state pages to see how this bridge ranks against its peers.
Every figure on this page comes directly from the Federal Highway Administration National Bridge Inventory (NBI), the public dataset that catalogs more than 617,000 highway bridges across the United States and is updated annually from the records that each state Department of Transportation submits to the FHWA. The condition codes use the standardized FHWA Recording and Coding Guide, the same scale that determines federal eligibility for the Highway Bridge Program and the Surface Transportation Block Grant set-aside for off-system bridges. A "structurally deficient" classification under those federal criteria is a maintenance and funding flag, never a closure order; states keep deficient bridges open with load posting, weight limits, or accelerated inspection cycles until rehabilitation or replacement is funded. See our methodology for refresh cadence and the exact NBI release vintage powering each record.
How A50 (BRIDGE ST) compares
NBI inventory load rating (metric tons) and structural-deficiency status compared across Iowa, computed live from the FHWA NBI.
Condition Ratings
Ratings are on a 0–9 scale: 9 = Excellent, 7–8 = Good, 5–6 = Fair, 3–4 = Poor, 0–2 = Critical/Failed. Sufficiency rating (0–100) combines structural adequacy, functional obsolescence, and essentiality.
Structural Details
- Year Built
- 1971
- Material
- Steel Continuous
- Number of Spans
- 4
- Structure Length
- 106.1 m (348 ft)
- Deck Width
- 9.8 m (32 ft)
- Owner
- County Highway Agency
- Avg Daily Traffic
- 888 vehicles/day
- Structure Number
- 000000000229541
Location
Data Source
Data from the FHWA National Bridge Inventory (NBI). Bridge inspections are required every two years by federal law. Conditions reflect the most recent inspection.
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Guides
Condition Analysis
Built in 1971, this bridge is 55 years old. It carries approximately 888 vehicles per day. Based on the most recent FHWA inspection:
- • The deck (driving surface) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
- • The superstructure (beams and supports above the deck) is in good condition (7/9), showing no significant deterioration.
- • The substructure (piers and abutments) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
Its NBI inventory load rating reflects the load level it is rated to carry.
Frequently Asked Questions
What do the condition ratings mean for A50 (BRIDGE ST)?
Bridge condition ratings use a 0–9 scale set by the Federal Highway Administration (FHWA). Ratings 7–9 indicate good condition with no significant problems. Ratings 5–6 mean fair condition with minor issues. Ratings 3–4 indicate poor condition requiring repair. Ratings 0–2 are critical, meaning the bridge has serious structural problems. A50 (BRIDGE ST) in Lyon, Iowa has a deck rating of 5/9, superstructure rating of 7/9, and substructure rating of 5/9.
How often is A50 (BRIDGE ST) inspected?
Federal law requires most highway bridges to be inspected at least every 24 months. Bridges in poor condition or with known issues may be inspected more frequently (every 12 months or less). A50 (BRIDGE ST) is part of the National Bridge Inventory maintained by the FHWA. With 888 vehicles crossing daily, regular inspection is essential.
What does "structurally deficient" mean for a bridge?
A structurally deficient bridge has at least one major component (deck, superstructure, or substructure) rated 4 or below on the FHWA 0–9 scale. This classification does NOT mean the bridge is unsafe for travel — it means the bridge needs repair, rehabilitation, or eventual replacement. Structurally deficient bridges remain open and are monitored. A50 (BRIDGE ST) is not classified as structurally deficient.
What is the inventory load rating for A50 (BRIDGE ST)?
The NBI inventory rating is the load level a bridge is rated to carry for an indefinite period, recorded in metric tons. A lower number means the structure is more load-restricted. A50 (BRIDGE ST) has an inventory load rating of 29.2 metric tons. It is distinct from the FHWA sufficiency rating, a separate 0–100 funding-eligibility score that this dataset does not include.
Who is responsible for maintaining A50 (BRIDGE ST)?
Bridge ownership and maintenance responsibility varies — bridges may be owned by state DOTs, counties, cities, railroads, or federal agencies. A50 (BRIDGE ST) is maintained by County Highway Agency. The FHWA oversees the National Bridge Inventory program and sets inspection standards, but day-to-day maintenance falls to the owning agency. If you notice damage or safety concerns, contact your state DOT or call 911 for emergencies.
How old is A50 (BRIDGE ST) and does age affect safety?
A50 (BRIDGE ST) was built in 1971, making it 55 years old. Bridge age alone does not determine safety — condition depends on materials, design, traffic load, maintenance history, and environmental exposure. Many older bridges remain in good condition due to regular maintenance and reconstruction.
Disclaimer: Bridge condition data is from the FHWA NBI and reflects the last reported inspection. A structurally deficient rating does not mean a bridge is closed or unsafe for travel — it indicates the bridge requires repair or replacement. For current closure or safety information, contact your state DOT.
Read our methodology — how this data is sourced, computed, and verified.
Related
| Publisher | Kiznis Studio |
| Sources | FHWA National Bridge Inventory, public U.S. government datasets |