SR 717
Carrying SR 717 over MILL RIVER
0.3 MI E OF ROUTE 10, Unknown County, Connecticut
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
SR 717 in Unknown County, Connecticut sits above 15% of rated Connecticut bridges on inventory load rating (31 t), while its 1948 build year is earlier than 80% of Unknown County's recorded-year cohort (893 bridges).
SR 717 in Unknown County, Connecticut is rated Fair in the FHWA's 2024 National Bridge Inventory. Built in 1948, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 6. 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:01660
PRE-1950 · STEEL · MULTI-SPAN · SUB-LED · HEAVY-ADT · STANDARD-LOAD · CAT-FAIR
- PRE-1950 Pre-1950
- STEEL Steel
- MULTI-SPAN 2 spans
- SUB-LED Substructure-led
- HEAVY-ADT Heavy ADT
- STANDARD-LOAD Standard 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: SR 717
The SR 717 bridge in Unknown County, Connecticut carries SR 717 over MILL RIVER. It was built in 1948, making it 78 years old today. It was last reconstructed in 1989, extending its service life. The structure is built primarily of steel and spans 2 sections, stretching 21.6 meters (71 feet) end to end. Daily traffic averages 18,600 vehicles, placing it in the heavily-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). None of this bridge's reported major components fall into the Poor condition range.
How SR 717 compares
Age against the county: built in 1948, earlier than 712 of Unknown County's 893 bridges with a recorded construction year (80%), against a county median build year of 1965. 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).
SR 717 vs every rated Connecticut bridge
Inventory load rating (metric tons), FHWA NBI, this state
31 Top 85% higher than 15% 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 893 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
- 1948
- Last Reconstructed
- 1989
- Material
- Steel
- Number of Spans
- 2
- Structure Length
- 21.6 m (71 ft)
- Deck Width
- 13.6 m (45 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 18,600 vehicles/day
- Structure Number
- 01660
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 good at 7/9, with no significant deterioration on file.
- • The substructure (piers and abutments) is in fair condition (6/9), with minor deterioration that may require routine maintenance.
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 SR 717 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 SR 717 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 SR 717?
SR 717 in Unknown County, Connecticut has a deck rating of 7/9, superstructure rating of 7/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is SR 717 inspected?
SR 717'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 18,600 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. SR 717 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 SR 717?
SR 717 has an NBI inventory load rating of 30.8 metric tons.
Who is responsible for maintaining SR 717?
SR 717 is owned and maintained by State Highway Agency.
How old is SR 717 and does age affect safety?
SR 717 was built in 1948, making it 78 years old and last reconstructed in 1989.
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.