County profile · official public datasets

Suffolk County, MA

489 public highway bridges tracked in the FHWA National Bridge Inventory: 22.7% rated Good, 67.7% Fair, 9.6% Poor.

489
Public bridges: 22.7%
Good condition: 9.6%
Poor condition

The verdict

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

Suffolk 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.

10th
of 13 on Poor share: 9.6%
Poor-condition share: 489
public highway bridges: 1967
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 #10 of 13 Massachusetts counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.6%). Suffolk County, Massachusetts contains 489 public highway bridges. Roughly 22.7% are rated “Good,” 67.7% “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

489

Public highway bridges in Suffolk County

Good condition

22.7%

111 of 489 rated 7-9

Fair condition

67.7%

331 of 489 rated 5-6

Poor condition

9.6%

47 of 489 rated 4 or below

In-state Poor-share rank

#10 of 13

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

Condition distribution

Share of 489 NBI-tracked bridges by lowest applicable component rating.

Good

22.7% (111)

Fair

67.7% (331)

Poor

9.6% (47)

Suffolk County's Poor-condition bridges carry 1,298,956 vehicle crossings a day

That is 7.9% of the county's reported daily bridge traffic on 9.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 27,637 crossings a day against 23,361 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 473 of 489 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

54.5% of Suffolk County's bridges have passed the 50-year mark

266 of the 488 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 22.7% 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 6.1% of the county's Poor-condition bridge traffic

HWY MORRSSEY BLV over WATER DORCHESTER BAY, built 1927, carries 78,900 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 47-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,298,956 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

24
1900s

26
1910s

18
1920s

13
1930s

19
1940s

1
1950s

83
1960s

52
1970s

36
1980s

26
1990s

55
2000s

127
2010s

8

What this shows Construction peaked in the 2000s, when 127 of the county's bridges still in the inventory were built, which is 26% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1967, 6 years newer than the Massachusetts average of 1961.

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

The 5 Massachusetts counties nearest Suffolk 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 1967 against a peer-group mean of 1960 is 7 years newer.

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

Bridge inventory size and condition shares for Suffolk County and the 5 Massachusetts counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Suffolk County (this page)	489	22.7%	67.7%	9.6%	1967
Berkshire County	450	34.7%	57.6%	7.8%	1961
Hampden County	428	17.1%	75.5%	7.5%	1956
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

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 Massachusetts so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MA (489 bridges here).

Black Hawk County, IA · 489 bridges
Shasta County, CA · 492 bridges
Lyon County, KS · 492 bridges
St. Clair County, IL · 486 bridges

Similar average build year

Nearest mean year-built outside MA (1967 here).

Los Angeles County, CA · avg 1967 · 3,547 bridges
Allegheny County, PA · avg 1967 · 1,294 bridges
Sonoma County, CA · avg 1967 · 609 bridges
Merced County, CA · avg 1967 · 528 bridges

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

All 489 Good 111 Fair 331 Poor 47

Good-condition bridges (111)

Sort:

Suffolk County Bridge Snapshot

Condition distribution

Suffolk County's Poor-condition bridges carry 1,298,956 vehicle crossings a day

54.5% of Suffolk County's bridges have passed the 50-year mark

One structure carries 6.1% of the county's Poor-condition bridge traffic

How Suffolk 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 (111)

HWY PARK ST

ST 28 LEVERETT CIR

HWY SO STA CONN

I 93 RMPS X XE

HWY SO STA CONN

I 93 RAMP N-S

HWY BEACH ST

I 90 RAMP F

HWY DARTMOUTH ST

HWY HARVARD ST

HWY FREIGHT COR

HWY S BOS BYPASS

ST145 REV BCH PKWY

HWY RESERVATN RD

I 93 NB

HWY N WSHNGTN ST

I 93 RAMP AS

HWY SUMMER ST

HWY SUMMER ST

HWY CHELSEA ST

I 93 RAMP SN

HWY BELLNGHM ST

HWY CUMMINS HWY

HWY D ST

I 90 RAMP D

I 93 RAMP LC-N

HWY VIADUCT ST

HWY DANA AVE

HWY SUMMER ST

US 20 COMM AV/MBTA

HWY RAMP L

HWY SO STA CONN

US 1 RP ABUT-BT50

HWY RAMP K/L

I 93 NB

HWY RAMP U-A

ST 1 A/RP E-1ASB

HWY RAMP K

HWY ALBANY EXT

I 93 RAMP FX

I 93 HOV RAMP EB

I 93 RAMP X

US 1 NB/S ABT PR1

I 90 EB & RP1ANB

HWY SO STA OB RP

ST 1 A/SB

ST 1 A/SB

US 1 RAMP S-TB

I 90 WB & RP1ASB

I 93 RAMP NS

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