FM - BOSTON
Carrying FM - BOSTON over NISHNABOTNA RIVER
077361205, Cass, Iowa
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: FM - BOSTON
The FM - BOSTON bridge in Cass, Iowa carries FM - BOSTON over NISHNABOTNA RIVER. It was built in 1951, making it 75 years old today. The structure is built primarily of steel continuous and spans 3 sections, stretching 64.9 meters (213 feet) end to end. Daily traffic averages 131 vehicles, placing it in the lower-traffic tier of Iowa bridges. It is owned and maintained by County Highway Agency.
The latest FHWA inspection records show a deck rating of 4/9, superstructure at 5/9, substructure at 4/9. The weakest component sits in poor condition. Because at least one major component scores 4 or lower, this bridge falls in FHWA's Poor condition category. That category is not a closure order. Its NBI inventory load rating is 17.5 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How FM - BOSTON compares
Live comparison across Iowa.
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 How the historical reference is calculated.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
- 1951
- Material
- Steel Continuous
- Number of Spans
- 3
- Structure Length
- 64.9 m (213 ft)
- Deck Width
- 6.7 m (22 ft)
- Owner
- County Highway Agency
- Avg Daily Traffic
- 131 vehicles/day
- Structure Number
- 000000000100960
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • At 4/9, the deck (driving surface) is in poor shape, with advanced wear flagged for priority repair.
- • The superstructure (beams and supports above the deck) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
- • The substructure (piers and abutments) is in poor condition (4/9), showing advanced deterioration that may require priority repair.
How to read this record
FM - BOSTON is in the federal Poor condition category. That is a component-based result, not a closure order.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Understand what Poor condition does and does not mean before drawing conclusions. Poor condition explained
- Compare FM - BOSTON against other structures in Cass and across Iowa. Iowa 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 FM - BOSTON?
FM - BOSTON in Cass, Iowa has a deck rating of 4/9, superstructure rating of 5/9, and substructure rating of 4/9 on the FHWA's 0–9 scale.
How often is FM - BOSTON inspected?
FM - BOSTON'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 131 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. FM - BOSTON is currently shown as Poor condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for FM - BOSTON?
FM - BOSTON has an NBI inventory load rating of 17.5 metric tons.
Who is responsible for maintaining FM - BOSTON?
FM - BOSTON is owned and maintained by County Highway Agency.
How old is FM - BOSTON and does age affect safety?
FM - BOSTON was built in 1951, making it 75 years old.
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.