County profile · official public datasets

Dorchester County, SC

198 public highway bridges tracked in the FHWA National Bridge Inventory: 28.8% rated Good, 69.2% Fair, 2% Poor.

198
Public bridges: 28.8%
Good condition: 2%
Poor condition

The verdict

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

Dorchester County pairs a top-quartile lowest Poor-condition share among rated counties in the state with an older average build year than the state inventory.

Top 11%
lowest Poor share in state: 2%
Poor-condition share: 198
public highway bridges: 1972
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.

Dorchester County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Dorchester County ranks #5 of 46 South Carolina counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 2%). Dorchester County, South Carolina contains 198 public highway bridges. Roughly 28.8% are rated “Good,” 69.2% “Fair,” and 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.

Total bridges

198

Public highway bridges in Dorchester County

Good condition

28.8%

57 of 198 rated 7-9

Fair condition

69.2%

137 of 198 rated 5-6

Poor condition

4 of 198 rated 4 or below

In-state Poor-share rank

#5 of 46

Among South Carolina counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 198 NBI-tracked bridges by lowest applicable component rating.

Good

28.8% (57)

Fair

69.2% (137)

Poor

2% (4)

Dorchester County's Poor-condition bridges carry 11,825 vehicle crossings a day

That is 0.8% of the county's reported daily bridge traffic on 2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,956 crossings a day against 6,100 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 198 of 198 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

65.7% of Dorchester County's bridges have passed the 50-year mark

130 of the 198 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 28.8% 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 66.8% of the county's Poor-condition bridge traffic

US 78 over FOUR HOLE SWAMP, built 1948, carries 7,900 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 4-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 11,825 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

3
1920s

11
1930s

12
1940s

4
1950s

19
1960s

44
1970s

43
1980s

13
1990s

12
2000s

23
2010s

11
2020s

3

What this shows Construction peaked in the 1960s, when 44 of the county's bridges still in the inventory were built, which is 22.2% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1972, 5 years older than the South Carolina average of 1977.

How Dorchester County compares with South Carolina's closest counties by inventory size

The 5 South Carolina counties nearest Dorchester County in number of bridges, with their condition splits. Its 2% Poor share is the 1st-lowest of these 6. Its average build year of 1972 against a peer-group mean of 1977 is 5 years older.

Showing the 5 closest of 45 South Carolina counties eligible for comparison.

Bridge inventory size and condition shares for Dorchester County and the 5 South Carolina counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Cherokee County	199	45.2%	43.7%	11.1%	1983
Chesterfield County	199	40.2%	54.8%	5%	1974
Aiken County	198	36.9%	53.5%	9.6%	1977
Dorchester County (this page)	198	28.8%	69.2%	2%	1972
Williamsburg County	195	38.5%	54.9%	6.7%	1977
Chester County	190	40.5%	50%	9.5%	1976

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 Dorchester 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 Dorchester County, both outside South Carolina so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SC (198 bridges here).

Scott County, AR · 198 bridges
Fulton County, OH · 198 bridges
Madison County, OH · 198 bridges
Erath County, TX · 198 bridges

Similar average build year

Nearest mean year-built outside SC (1972 here).

Santa Clara County, CA · avg 1972 · 964 bridges
Madison County, AL · avg 1972 · 710 bridges
Kern County, CA · avg 1972 · 668 bridges
York County, PA · avg 1972 · 569 bridges

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

All 198 Good 57 Fair 137 Poor 4

All bridges (198)

Sort:

Dorchester County Bridge Snapshot

Condition distribution

Dorchester County's Poor-condition bridges carry 11,825 vehicle crossings a day

65.7% of Dorchester County's bridges have passed the 50-year mark

One structure carries 66.8% of the county's Poor-condition bridge traffic

How Dorchester County compares with South Carolina'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 (198)

I-95

I-95 NB

I-95 SB

I-26 EB

I-26 WB

I-26 EB

I-26 WB

I-95 NB

I-95 SB

S-18-54

S-18-86/MTZION RD

SC 453/JUDGE ST

S-18-11

S-18-18

I-95 NB

I-95 SB

I-95 NB

I-95 NB

I-95 NB

I-95 SB

I-95 SB

I-95 SB

S-18-25/ZION RD

SC 61

S-18-136

S-18-199

I-95 SB

SC 642

I-95 NB

I-95 NB

I-95 SB

C-18-1032

SC 165

S-18-610/ALONZO RD

I-95 NB

I-95 SB

C-18-136

SC 61

SC 27/GIVHANS RD

US 17 ALT

S-163/SUMMERS DR

SC 165

SC 165

US 178/E MAIN ST

S-18-29

SC 165

S-18-135/SMOAK RD

S-18-180

S-18-83

S-18-83

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