County profile · official public datasets

Somerset County, NJ

397 public highway bridges tracked in the FHWA National Bridge Inventory: 33% rated Good, 57.4% Fair, 9.6% Poor.

397
Public bridges: 33%
Good condition: 9.6%
Poor condition

The verdict

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

Somerset County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

19th
of 21 on Poor share: 9.6%
Poor-condition share: 397
public highway bridges: 1970
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.

Somerset County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Somerset County ranks #19 of 21 New Jersey counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.6%). Somerset County, New Jersey contains 397 public highway bridges. Roughly 33% are rated “Good,” 57.4% “Fair,” and 9.6% “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

397

Public highway bridges in Somerset County

Good condition

33%

131 of 397 rated 7-9

Fair condition

57.4%

228 of 397 rated 5-6

Poor condition

9.6%

38 of 397 rated 4 or below

In-state Poor-share rank

#19 of 21

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

Condition distribution

Share of 397 NBI-tracked bridges by lowest applicable component rating.

Good

33% (131)

Fair

57.4% (228)

Poor

9.6% (38)

Somerset County's Poor-condition bridges carry 639,320 vehicle crossings a day

That is 10% of the county's reported daily bridge traffic on 9.6% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 16,824 crossings a day against 9,020 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 397 of 397 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

54.2% of Somerset County's bridges have passed the 50-year mark

215 of the 397 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 33% 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 9.2% of the county's Poor-condition bridge traffic

I-78 EASTBOUND over I-78 RAMP "A", built 1963, carries 58,865 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 38-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 639,320 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

11
1900s

9
1910s

12
1920s

24
1930s

15
1940s

14
1950s

15
1960s

108
1970s

29
1980s

27
1990s

46
2000s

51
2010s

27
2020s

9

What this shows Construction peaked in the 1960s, when 108 of the county's bridges still in the inventory were built, which is 27.2% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1970) matches the New Jersey average (1966).

How Somerset County compares with New Jersey's closest counties by inventory size

The 5 New Jersey counties nearest Somerset County in number of bridges, with their condition splits. Its 9.6% Poor share is the 5th-lowest of these 6. Its average build year of 1970 against a peer-group mean of 1965 is 5 years newer.

Showing the 5 closest of 20 New Jersey counties eligible for comparison.

Bridge inventory size and condition shares for Somerset County and the 5 New Jersey counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Mercer County	414	40.3%	50.5%	9.2%	1975
Union County	409	17.8%	78%	4.2%	1967
Somerset County (this page)	397	33%	57.4%	9.6%	1970
Hunterdon County	373	20.1%	72.4%	7.5%	1949
Burlington County	356	26.4%	63.5%	10.1%	1969
Passaic County	333	22.2%	74.5%	3.3%	1963

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 Somerset 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 Somerset County, both outside New Jersey so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside NJ (397 bridges here).

Muskogee County, OK · 398 bridges
Sumner County, TN · 398 bridges
Humboldt County, CA · 396 bridges
Nodaway County, MO · 396 bridges

Similar average build year

Nearest mean year-built outside NJ (1970 here).

Hamilton County, OH · avg 1970 · 783 bridges
Yavapai County, AZ · avg 1970 · 543 bridges
Garfield County, OK · avg 1970 · 504 bridges
San Luis Obispo County, CA · avg 1970 · 401 bridges

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

All 397 Good 131 Fair 228 Poor 38

Fair-condition bridges (228)

Sort:

Somerset County Bridge Snapshot

Condition distribution

Somerset County's Poor-condition bridges carry 639,320 vehicle crossings a day

54.2% of Somerset County's bridges have passed the 50-year mark

One structure carries 9.2% of the county's Poor-condition bridge traffic

How Somerset County compares with New Jersey's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (228)

I-287 NB

GROVE STREET

MINE BROOK ROAD

I-78 EB

I-78 WB

I-78 EASTBOUND

GARRETSON ROAD

VOSSELLER AVENUE

KING GEORGE RD

REINMAN ROAD

US 206

I-287 SB

LIBERTY CORNER RD

I-287 SB

I-78 EB

US 206

ROUTE I-287 N.B.

ROUTE I-287 S.B.

I-287 NB

LIBERTY CORNER RD.

OLD STIRLING ROAD

PLESNT RUN RD(629)

ANDRIA AVENUE

COUNTY ROUTE 512

US 22 WB

NJ 28

MT AIRY RD CR 525

FALCON ROAD

US 206

COUNTY ROUTE 512

US 22 WB

I-287 NORTHBOUND

NORTH BRIDGE ST

I-78 WB

ZION-WERTSVILLE RD

WARRENVILLE RD

RT NJ 28

US 206

CEDAR BROOK RD

I-78 EB.

Martinsville Rd SB

WHALEN STREET

WASHINGTON AVE.

INTERHAVEN AVENUE

US 22

MOUNTAIN AVENUE

ROCK AVE (CR 645)

BUNN RD

Saw Mill Road

NORTH BRIDGE ST

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