Total bridges
414
Public highway bridges in Mercer County
County profile · official public datasets
Mercer County, NJ
414 public highway bridges tracked in the FHWA National Bridge Inventory: 40.3% rated Good, 50.5% Fair, 9.2% Poor.
- 414
- Public bridges
- 40.3%
- Good condition
- 9.2%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Mercer County pairs a higher-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- 17th
- of 21 on Poor share
- 9.2%
- Poor-condition share
- 414
- public highway bridges
- 1975
- 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.
Mercer County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Mercer County ranks #17 of 21 New Jersey counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.2%). Mercer County, New Jersey contains 414 public highway bridges. Roughly 40.3% are rated “Good,” 50.5% “Fair,” and 9.2% “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.
Good condition
40.3%
167 of 414 rated 7-9
Fair condition
50.5%
209 of 414 rated 5-6
Poor condition
9.2%
38 of 414 rated 4 or below
In-state Poor-share rank
#17 of 21
Among New Jersey counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 414 NBI-tracked bridges by lowest applicable component rating.
Good 40.3% (167)
Fair 50.5% (209)
Poor 9.2% (38)
Mercer County's Poor-condition bridges carry 408,944 vehicle crossings a day
That is 4.8% of the county's reported daily bridge traffic on 9.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 10,762 crossings a day against 18,074 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 414 of 414 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
46.6% of Mercer County's bridges have passed the 50-year mark
192 of the 412 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 40.3% 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 10.3% of the county's Poor-condition bridge traffic
US ROUTE 1 over D&R CANAL, built 1973, carries 42,271 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 408,944 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Mercer County's bridges were built
412 bridges with a recorded construction year, grouped by decade
- pre-1900 9
Built before 1900
9 bridges
- 1900s 9
1900–1909
9 bridges
- 1910s 13
1910–1919
13 bridges
- 1920s 16
1920–1929
16 bridges
- 1930s 16
1930–1939
16 bridges
- 1940s 6
1940–1949
6 bridges
- 1950s
1950–1959
45 bridges
- 1960s 23
1960–1969
23 bridges
- 1970s
1970–1979
65 bridges
- 1980s
1980–1989
39 bridges
- 1990s
1990–1999
52 bridges
- 2000s 26
2000–2009
26 bridges
- 2010s
2010–2019
89 bridges
- 2020s 4
2020–2029
4 bridges
What this shows Construction peaked in the 2010s, when 89 of the county's bridges still in the inventory were built, which is 21.6% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1975, 9 years newer than the New Jersey average of 1966.
How Mercer County compares with New Jersey's closest counties by inventory size
The 5 New Jersey counties nearest Mercer County in number of bridges, with their condition splits. Its 9.2% Poor share is the 4th-lowest of these 6. Its average build year of 1975 against a peer-group mean of 1964 is 11 years newer.
Showing the 5 closest of 20 New Jersey counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Mercer County (this page) | 414 | 40.3% | 50.5% | 9.2% | 1975 |
| Union County | 409 | 17.8% | 78% | 4.2% | 1967 |
| Somerset County | 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 Mercer 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 Mercer County, both outside New Jersey so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside NJ (414 bridges here).
- Cobb County, GA · 414 bridges
- Stark County, OH · 415 bridges
- Macomb County, MI · 417 bridges
- St. Charles County, MO · 417 bridges
Similar average build year
Nearest mean year-built outside NJ (1975 here).
- San Bernardino County, CA · avg 1975 · 1,422 bridges
- Lane County, OR · avg 1975 · 1,010 bridges
- Fulton County, GA · avg 1975 · 775 bridges
- Westmoreland County, PA · avg 1975 · 620 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (414)
SOUTH OLDEN AVENUE
PoorOver: AMTRAK NE CORRIDOR
0.55 MILES SOUTH OF US 1, Mercer, NJ
Built 1923 Load: 31.8 t ADT: 22,960
US 130
PoorOver: MILLSTONE RIVER
0.66 Mi. N of Rt 133 Jct, Mercer, NJ
Built 1936 Load: 35.4 t ADT: 32,898
NJ 64
PoorOver: AMTRAK
0.22 MI. S. of CR 571, Mercer, NJ
Built 1939 Load: 37.2 t ADT: 16,255
QUAKER BRIDGE ROAD
PoorOver: AMTRAK
1.3 MILES S OF ROUTE 1, Mercer, NJ
Built 1966 Load: 37.2 t ADT: 33,105
YARD ROAD
PoorOver: BALDWINS CREEK
0.3 MI WEST OF RT 31 JCT, Mercer, NJ
Built 1969 Load: 38.1 t ADT: 478
US 206 (N. BROAD)
PoorOver: D&R FEEDER CANAL
0.1 MI S OF 206&31 JCT, Mercer, NJ
Built 1917 Load: 38.1 t ADT: 5,391
PROSPECT STREET
PoorOver: SHABAKUNK CREEK
0.23 mile S. of Olden Ave, Mercer, NJ
Built 1930 Load: 41.7 t ADT: 14,195
PENN-CTRVILLE RD
PoorOver: STONY BROOK
0.69M S of CR 625, Mercer, NJ
Built 1987 Load: 45.4 t ADT: 7,072
CLARKSVILLE ROAD
PoorOver: AMTRAK NE CORRIDOR
1.98 MILES WEST OF RT 571, Mercer, NJ
Built 1900 Load: 45.4 t ADT: 15,867
NJ 29
PoorOver: NJ 175&D&R CANAL FEEDER
0.27 MI NORTH OF I-95 JCT, Mercer, NJ
Built 1960 Load: 49.0 t ADT: 13,593
US ROUTE 1
PoorOver: D&R CANAL
4.0 MILES NO.OF DEL.RIV., Mercer, NJ
Built 1973 Load: 52.6 t ADT: 42,271
Millstone Road
PoorOver: Millstone River
0.5 MI N.OF COUNTY RT 615, Mercer, NJ
Built 1967 Load: 53.5 t ADT: 8,430
PRINCETON PIKE
PoorOver: I-295 RAMPS B AND D
1 MI N OF US 1 & I295 JCT, Mercer, NJ
Built 1973 Load: 62.6 t ADT: 13,255
YRDVLLE-ALLNTWN RD
PoorOver: US 130
1.59 Mi W of NJ Turnpike, Mercer, NJ
Built 1951 Load: 64.4 t ADT: 12,226
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges 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. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.