County profile · official public datasets

Plymouth County, MA

287 public highway bridges tracked in the FHWA National Bridge Inventory: 30.7% rated Good, 63.4% Fair, 5.9% Poor.

287
Public bridges: 30.7%
Good condition: 5.9%
Poor condition

The verdict

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

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

Top 31%
lowest Poor share in state: 5.9%
Poor-condition share: 287
public highway bridges: 1960
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.

Plymouth County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Plymouth County ranks #4 of 13 Massachusetts counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.9%). Plymouth County, Massachusetts contains 287 public highway bridges. Roughly 30.7% are rated “Good,” 63.4% “Fair,” and 5.9% “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

287

Public highway bridges in Plymouth County

Good condition

30.7%

88 of 287 rated 7-9

Fair condition

63.4%

182 of 287 rated 5-6

Poor condition

5.9%

17 of 287 rated 4 or below

In-state Poor-share rank

#4 of 13

Among Massachusetts counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 287 NBI-tracked bridges by lowest applicable component rating.

Good

30.7% (88)

Fair

63.4% (182)

Poor

5.9% (17)

Plymouth County's Poor-condition bridges carry 293,076 vehicle crossings a day

That is 5.8% of the county's reported daily bridge traffic on 5.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 17,240 crossings a day against 14,834 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 286 of 287 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

67.9% of Plymouth County's bridges have passed the 50-year mark

195 of the 287 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 30.7% 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 24.2% of the county's Poor-condition bridge traffic

HWY CENTRAL ST over WATER SHUMATUSCACANT RIV, built 1956, carries 71,009 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 17-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 293,076 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

24
1900s

6
1910s

7
1920s

13
1930s

10
1940s

9
1950s

62
1960s

42
1970s

33
1980s

18
1990s

19
2000s

26
2010s

16
2020s

2

What this shows Construction peaked in the 1950s, when 62 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 65 to 74 years old in the 2024 inventory. Its average build year (1960) matches the Massachusetts average (1961).

How Plymouth County compares with Massachusetts's closest counties by inventory size

The 5 Massachusetts counties nearest Plymouth County in number of bridges, with their condition splits. Its 5.9% Poor share is the 2nd-lowest of these 6. Its average build year of 1960 against a peer-group mean of 1961 is in line with the group.

Showing the 5 closest of 12 Massachusetts counties eligible for comparison.

Bridge inventory size and condition shares for Plymouth County and the 5 Massachusetts counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Essex County	395	15.9%	66.8%	17.2%	1957
Bristol County	384	30.2%	63.3%	6.5%	1962
Norfolk County	343	23.6%	71.4%	5%	1962
Franklin County	314	34.4%	54.5%	11.1%	1964
Plymouth County (this page)	287	30.7%	63.4%	5.9%	1960
Hampshire County	259	25.1%	66%	8.9%	1959

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 Plymouth 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 Plymouth County, both outside Massachusetts so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MA (287 bridges here).

Chariton County, MO · 288 bridges
York County, SC · 288 bridges
Rockingham County, VA · 288 bridges
Haywood County, NC · 286 bridges

Similar average build year

Nearest mean year-built outside MA (1960 here).

Windham County, VT · avg 1960 · 337 bridges
Cheshire County, NH · avg 1960 · 192 bridges
Washington County, NY · avg 1960 · 189 bridges
Cherokee County, AL · avg 1960 · 167 bridges

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

All 287 Good 88 Fair 182 Poor 17

Good-condition bridges (88)

Sort:

Plymouth County Bridge Snapshot

Condition distribution

Plymouth County's Poor-condition bridges carry 293,076 vehicle crossings a day

67.9% of Plymouth County's bridges have passed the 50-year mark

One structure carries 24.2% of the county's Poor-condition bridge traffic

How Plymouth County compares with Massachusetts's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (88)

ST123 CENTER ST

HWY SCOTLAND ST

HWY CENTER ST

ST 18 BEDFORD ST

HWY WHITE AVE

US 44

HWY NEMASKET ST

HWY COMMERCE WAY

HWY STOCKBDGE RD

HWY CHERRY ST

HWY W ELM ST

ST 3 NB PLGM HWY

ST 3 SB PLGM HWY

ST 3 NB PLGM HWY

ST 3 SB PLGM HWY

HWY MAIN ST

HWY MAIN AVE

ST 18 BEDFORD ST

HWY SEA ST

HWY SOUTH ST

ST 3 NB/PLGRM HWY

ST 3 SB/PLGRM HWY

HWY PERKINS AVE

HWY ALLEN ST

HWY HIGHLAND RD

HWY SUMMER ST

HWY ELM ST

HWY STATE ST

HWY HIGHLAND RD

ST 25 EB

ST106 WAPPING RD

ST123 BELMONT ST

HWY JULIAN ST

HWY TAYLOR AVE

HWY FOREST ST

HWY COUNTRY WAY

HWY BROADWAY

US 6 EB/ST28 SB

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