ROUTE 171
Carrying ROUTE 171 over QUINEBAUG RIVER
.3 MI W OF US ROUTE 44, Unknown County, Connecticut
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
ROUTE 171 in Unknown County, Connecticut sits above 85% of rated Connecticut bridges on inventory load rating (58 t), while its 1952 build year is earlier than 65% of Unknown County's recorded-year cohort (267 bridges).
ROUTE 171 in Unknown County, Connecticut is rated Fair in the FHWA's 2024 National Bridge Inventory. Built in 1952, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 5. The lowest applicable rating sets the federal condition category, so this Fair result describes the weakest reported component rather than the structure as a whole. No NBI category is a closure decision or a live crossing-safety verdict.
NBI record plate
Structure CT:01424
INTERSTATE-ERA · STEEL · SINGLE-SPAN · SUPER-LED · ARTERIAL-ADT · HEAVY-LOAD · CAT-FAIR
- INTERSTATE-ERA 1950–1979
- STEEL Steel
- SINGLE-SPAN Single span
- SUPER-LED Superstructure-led
- ARTERIAL-ADT Arterial ADT
- HEAVY-LOAD Heavy load
- CAT-FAIR Fair
Inspection-sheet codes from this record’s year, material family, spans, controlling component, ADT, inventory load, and NBI category, not a live closure verdict.
Structural health score
A composite of the deck, superstructure, and substructure NBI condition ratings plus the inventory load rating, benchmarked against the full national bridge corpus, distinct from the Good/Fair/Poor category above.
Bridge Snapshot: ROUTE 171
The ROUTE 171 bridge in Unknown County, Connecticut carries ROUTE 171 over QUINEBAUG RIVER. It was built in 1952, making it 74 years old today. It was last reconstructed in 1988, extending its service life. The structure is built primarily of steel and spans 1 section, stretching 35.7 meters (117 feet) end to end. Daily traffic averages 9,700 vehicles, placing it in the moderately-trafficked tier of Connecticut bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection places the weakest component in fair condition (see the full component ratings below). No reported major component scores in the Poor range under the current federal condition thresholds.
How ROUTE 171 compares
Age against the county: built in 1952, earlier than 174 of Unknown County's 267 bridges with a recorded construction year (65%), against a county median build year of 1962. Age is not a defect on its own, but it is the population from which future Poor ratings are drawn.
Live comparison across Connecticut bridges with a recorded inventory load rating (4,365 rated).
ROUTE 171 vs every rated Connecticut bridge
Inventory load rating (metric tons), FHWA NBI, this state
58 Top 15% higher than 85% of 4,365 bridges
rated Connecticut bridges, bucketed by value
Each bar is a band; taller bars hold more bridges. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source FHWA National Bridge Inventory · August 2026
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Reported 0–9 component ratings from the FHWA NBI. The highlighted component is the lowest reported input to this record’s current condition category; it is not a closure or live crossing-safety decision.
Unknown County inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 267 bridges in this county. Orthogonal to this structure's component profile above: a county catalog share, not a live crossing-safety verdict.
Structural Details
- Year Built
- 1952
- Last Reconstructed
- 1988
- Material
- Steel
- Number of Spans
- 1
- Structure Length
- 35.7 m (117 ft)
- Deck Width
- 16.5 m (54 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 9,700 vehicles/day
- Structure Number
- 01424
Condition Analysis
- • At 7/9, the deck (driving surface) is in good shape and shows no significant wear.
- • The superstructure (beams and supports above the deck) rates fair at 5/9, minor deterioration that routine maintenance should address.
- • At 6/9, the substructure (piers and abutments) shows fair condition, with minor wear flagged for upkeep.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
This page shows what the last federal inspection recorded, not whether ROUTE 171 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 ROUTE 171 against other structures in Unknown County and across Connecticut. Connecticut 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 ROUTE 171?
ROUTE 171 in Unknown County, Connecticut has a deck rating of 7/9, superstructure rating of 5/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is ROUTE 171 inspected?
ROUTE 171'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 9,700 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. ROUTE 171 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 ROUTE 171?
ROUTE 171 has an NBI inventory load rating of 58.3 metric tons.
Who is responsible for maintaining ROUTE 171?
ROUTE 171 is owned and maintained by State Highway Agency.
How old is ROUTE 171 and does age affect safety?
ROUTE 171 was built in 1952, making it 74 years old and last reconstructed in 1988.
Share this inspection record
Send this source-bounded record or download its data card. An NBI condition category is not a closure or live crossing-safety verdict.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. Component ratings, ADT, and condition category on this page are copied from the NBI record for this structure; no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2024 NBI release. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.