County profile · official public datasets

Dauphin County, PA

449 public highway bridges tracked in the FHWA National Bridge Inventory: 22% rated Good, 69.5% Fair, 8.5% Poor.

449
Public bridges: 22%
Good condition: 8.5%
Poor condition

The verdict

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

Dauphin County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 25%
lowest Poor share in state: 8.5%
Poor-condition share: 449
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.

Dauphin County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Dauphin County ranks #17 of 67 Pennsylvania counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 8.5%). Dauphin County, Pennsylvania contains 449 public highway bridges. Roughly 22% are rated “Good,” 69.5% “Fair,” and 8.5% “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

449

Public highway bridges in Dauphin County

Good condition

22%

99 of 449 rated 7-9

Fair condition

69.5%

312 of 449 rated 5-6

Poor condition

8.5%

38 of 449 rated 4 or below

In-state Poor-share rank

#17 of 67

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

Condition distribution

Share of 449 NBI-tracked bridges by lowest applicable component rating.

Good

22% (99)

Fair

69.5% (312)

Poor

8.5% (38)

Dauphin County's Poor-condition bridges carry 282,999 vehicle crossings a day

That is 5.1% of the county's reported daily bridge traffic on 8.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 7,649 crossings a day against 11,791 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 446 of 449 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

56.6% of Dauphin County's bridges have passed the 50-year mark

254 of the 449 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% 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 30.1% of the county's Poor-condition bridge traffic

SR 0083; I-83 over SUSQ.RIVER;R.R.LOWTHER S, built 1960, carries 85,221 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 282,999 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

2
1900s

5
1910s

7
1920s

16
1930s

17
1940s

28
1950s

26
1960s

84
1970s

109
1980s

48
1990s

46
2000s

18
2010s

30
2020s

13

What this shows Construction peaked in the 1970s, when 109 of the county's bridges still in the inventory were built, which is 24.3% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1972) matches the Pennsylvania average (1970).

How Dauphin County compares with Pennsylvania's closest counties by inventory size

The 5 Pennsylvania counties nearest Dauphin County in number of bridges, with their condition splits. Its 8.5% Poor share is the 2nd-lowest of these 6. Its average build year of 1972 against a peer-group mean of 1973 is in line with the group.

Showing the 5 closest of 66 Pennsylvania counties eligible for comparison.

Bridge inventory size and condition shares for Dauphin County and the 5 Pennsylvania counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Luzerne County	457	28.9%	45.5%	25.6%	1972
Somerset County	454	33%	52.6%	14.3%	1969
Dauphin County (this page)	449	22%	69.5%	8.5%	1972
Erie County	442	37.8%	52.7%	9.5%	1976
Mercer County	438	39.3%	45.2%	15.5%	1972
Tioga County	429	49.4%	47.3%	3.3%	1977

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

Similar inventory size

Nearest county inventories outside PA (449 bridges here).

Washington County, AR · 449 bridges
Sioux County, IA · 449 bridges
Barton County, KS · 449 bridges
Grady County, OK · 449 bridges

Similar average build year

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

Santa Clara County, CA · avg 1972 · 964 bridges
Madison County, AL · avg 1972 · 710 bridges
Kern County, CA · avg 1972 · 668 bridges
Middlesex County, NJ · avg 1972 · 563 bridges

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

All 449 Good 99 Fair 312 Poor 38

Good-condition bridges (99)

Sort:

Dauphin County Bridge Snapshot

Condition distribution

Dauphin County's Poor-condition bridges carry 282,999 vehicle crossings a day

56.6% of Dauphin County's bridges have passed the 50-year mark

One structure carries 30.1% of the county's Poor-condition bridge traffic

How Dauphin County compares with Pennsylvania'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 (99)

PA 283; SR 0300

PA TPK (I-76)

SR 8001 RP E.

PA 283 WB (SR0300)

SR 8001 RAMP G I81

PA 283; SR 0300

PA 441; SR 0441

MATTER RD T-617

PA 443; SR 0443

T-601 Jonestown Rd

US 22 EB; SR 0022

T-494/SCHOOL HS RD

PA TPK (RAMP AB)

Schoolhouse Lane

T-467 Carlson Road

PA 283; SR 0300

PA TPK (I-76)

PA 39; SR 0039

SR 2003

PA 147; SR 0147

T570;MAPLEDALE RD

T495;MCINTOSH RD

PA 39; SR 0039

SR 3021; TWP RD

SR 2017

I-83; SR 0083

SR 3012 Market St.

SR 2017

T-382 Baker Ave.

SR 3020

US 22; SR 0022

Bonnymeade Ave.

T-690 Duke Street

I-81 NB; SR 0081

SR 1021

US 322; SR 0322

Powells Valley Rd

POTATO VALLEY RD.

SR3026;Elmerton Av

PA TPK (I-76)

SR 2030

PA TPK (I-76)

Manda Bott Rd

US 209; SR 0209

US 22; SR 0022 WB

US 22; SR 0022 EB

I-83; SR 0083

PA 283; SR 0300

Rutter Rd (SR4004)

PA TPK (I-76)

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