County profile · official public datasets

Suffolk County, NY

369 public highway bridges tracked in the FHWA National Bridge Inventory: 27.1% rated Good, 71.5% Fair, 1.4% Poor.

369
Public bridges: 27.1%
Good condition: 1.4%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Suffolk County posts a top-5% lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 3%
lowest Poor share in state: 1.4%
Poor-condition share: 369
public highway bridges: 1968
avg year built

Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.

Suffolk County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Suffolk County ranks #2 of 62 New York counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 1.4%). Suffolk County, New York contains 369 public highway bridges. Roughly 27.1% are rated “Good,” 71.5% “Fair,” and 1.4% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.

Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

Total bridges

369

Public highway bridges in Suffolk County

Good condition

27.1%

100 of 369 rated 7-9

Fair condition

71.5%

264 of 369 rated 5-6

Poor condition

1.4%

5 of 369 rated 4 or below

In-state Poor-share rank

#2 of 62

Among New York counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 369 NBI-tracked bridges by lowest applicable component rating.

Good

27.1% (100)

Fair

71.5% (264)

Poor

1.4% (5)

Suffolk County's Poor-condition bridges carry 54,548 vehicle crossings a day

That is 0.6% of the county's reported daily bridge traffic on 1.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 13,637 crossings a day against 25,957 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.

Computed over the 366 of 369 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

71.3% of Suffolk County's bridges have passed the 50-year mark

263 of the 369 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 27.1% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.

Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.

One structure carries 71.8% of the county's Poor-condition bridge traffic

RTE 27 over NORTH RD, built 1959, carries 39,182 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 5-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 54,548 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

3
1900s

3
1910s

4
1920s

6
1930s

14
1940s

24
1950s

47
1960s

96
1970s

84
1980s

18
1990s

47
2000s

10
2010s

10
2020s

3

What this shows Construction peaked in the 1960s, when 96 of the county's bridges still in the inventory were built, which is 26% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1968) matches the New York average (1972).

How Suffolk County compares with New York's closest counties by inventory size

The 5 New York counties nearest Suffolk County in number of bridges, with their condition splits. Its 1.4% Poor share is the 1st-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1974 is 6 years older.

Showing the 5 closest of 61 New York counties eligible for comparison.

Bridge inventory size and condition shares for Suffolk County and the 5 New York counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Allegany County	402	39.1%	54.7%	6.2%	1981
Ulster County	392	21.7%	57.4%	20.9%	1974
Suffolk County (this page)	369	27.1%	71.5%	1.4%	1968
Sullivan County	365	39.2%	53.2%	7.7%	1975
Albany County	343	29.7%	65%	5.2%	1975
Dutchess County	332	22.6%	60.8%	16.6%	1967

Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Suffolk County's. Source: FHWA National Bridge Inventory, 2024 release.

Nationwide counties with similar inventory size or average build year

Two NBI-derived peer sets for Suffolk County, both outside New York so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside NY (369 bridges here).

Saline County, KS · 369 bridges
Cass County, ND · 369 bridges
Waukesha County, WI · 369 bridges
Collier County, FL · 370 bridges

Similar average build year

Nearest mean year-built outside NY (1968 here).

Montgomery County, PA · avg 1968 · 828 bridges
San Joaquin County, CA · avg 1968 · 644 bridges
Providence County, RI · avg 1968 · 476 bridges
Imperial County, CA · avg 1968 · 444 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 369 Good 100 Fair 264 Poor 5

All bridges (369)

Sort:

Suffolk County Bridge Snapshot

Condition distribution

Suffolk County's Poor-condition bridges carry 54,548 vehicle crossings a day

71.3% of Suffolk County's bridges have passed the 50-year mark

One structure carries 71.8% of the county's Poor-condition bridge traffic

How Suffolk County compares with New York's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (369)

RTE I495

RTE I495

RTE I495

RTE I495

RTE I495

27 SERVICE RD

WOODSIDE AVE

RTE I495

RTE 906A

SHORE DR

RTE 27

NICOLLS ROAD SB

NICOLLS ROAD NB

RTE 27

DEER PARK AVE

YAPHANK AVENUE

PECONIC ROAD

RTE 231

RTE 231

RTE 110

RTE 27

PORT JEFFERSON RD

RTE 109

RTE 109

RTE I495

RTE 906A

BRENTWOOD ROAD

RTE 908J

RTE 908K

PORT JEFFERSON RD

OLD NICHOLS RD

HIGBIE LANE

NORTH OCEAN AVE

RTE 27

RTE 27A

RTE I495

HOLBROOK RD

RTE 908M

RTE 908M

RED BRIDGE RD

WOODSIDE AVE

RTE 25

SGSP SB TO SSP EB

SYLVAN RD

WAVERLY AVENUE

NICOLLS ROAD SB

NICOLLS ROAD NB

SILLS ROAD

SILLS RD NB

BELLPORT AVENUE

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