County profile · official public datasets

Marion County, IN

958 public highway bridges tracked in the FHWA National Bridge Inventory: 45.9% rated Good, 49.5% Fair, 4.6% Poor.

Compiled by PlainBridges

958
Public bridges: 45.9%
Good condition: 4.6%
Poor condition

The verdict

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

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

Top 47%
lowest Poor share in state: 4.6%
Poor-condition share: 958
public highway bridges: 1976
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.

Marion County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Marion County ranks #43 of 92 Indiana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4.6%). Marion County, Indiana contains 958 public highway bridges. Roughly 45.9% are rated “Good,” 49.5% “Fair,” and 4.6% “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

958

Public highway bridges in Marion County

Good condition

45.9%

440 of 958 rated 7-9

Fair condition

49.5%

474 of 958 rated 5-6

Poor condition

4.6%

44 of 958 rated 4 or below

In-state Poor-share rank

#43 of 92

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

Condition distribution

Share of 958 NBI-tracked bridges by lowest applicable component rating.

Good

45.9% (440)

Fair

49.5% (474)

Poor

4.6% (44)

Marion County's Poor-condition bridges carry 697,793 vehicle crossings a day

That is 2.7% of the county's reported daily bridge traffic on 4.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 15,859 crossings a day against 30,399 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 958 of 958 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

60.3% of Marion County's bridges have passed the 50-year mark

578 of the 958 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 45.9% 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 18.5% of the county's Poor-condition bridge traffic

I-465 over DELAWARE CREEK, built 1966, carries 129,314 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 44-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 697,793 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

12
1910s

12
1920s

24
1930s

24
1940s

19
1950s

86
1960s

276
1970s

159
1980s

47
1990s

72
2000s

96
2010s

56
2020s

74

What this shows Construction peaked in the 1960s, when 276 of the county's bridges still in the inventory were built, which is 28.8% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1976) matches the Indiana average (1978).

How Marion County compares with Indiana's closest counties by inventory size

The 5 Indiana counties nearest Marion County in number of bridges, with their condition splits. Its 4.6% Poor share is the 4th-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1984 is 8 years older.

Showing the 5 closest of 91 Indiana counties eligible for comparison.

Bridge inventory size and condition shares for Marion County and the 5 Indiana counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Marion County (this page)	958	45.9%	49.5%	4.6%	1976
Allen County	613	41.6%	51.5%	6.9%	1978
Lake County	501	51.1%	42.9%	6%	1984
Hamilton County	454	68.3%	29.1%	2.6%	1996
Gibson County	362	42.8%	53%	4.1%	1978
Hendricks County	355	41.4%	56.3%	2.3%	1982

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

Similar inventory size

Nearest county inventories outside IN (958 bridges here).

Santa Clara County, CA · 964 bridges
Hennepin County, MN · 936 bridges
Jackson County, MO · 930 bridges
Denton County, TX · 991 bridges

Similar average build year

Nearest mean year-built outside IN (1976 here).

Mohave County, AZ · avg 1976 · 641 bridges
Comanche County, OK · avg 1976 · 593 bridges
Prince George's County, MD · avg 1976 · 576 bridges
New Castle County, DE · avg 1976 · 527 bridges

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

All 958 Good 440 Fair 474 Poor 44

All bridges (958)

Sort:

Marion County Bridge Snapshot

Condition distribution

Marion County's Poor-condition bridges carry 697,793 vehicle crossings a day

60.3% of Marion County's bridges have passed the 50-year mark

One structure carries 18.5% of the county's Poor-condition bridge traffic

How Marion County compares with Indiana'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 (958)

I-70 WB & I-65 SB

I-70 EB ON RAMP

I-465 NB

N. BLACKFORD ST.

SAM JONES EXPRWY

I-465 SB

I-465 WB TO I-65 S

EMERSON AVENUE

I-70

RAMP I465SB-I70EB

SOUTHEASTERN AVE

NB SHADELAND RAMP

OAKLANDON RD

RAMP I69SB TO I465

NW LOOP RAMP TO I-

FARLEY RD

I-70 EB

I-465 NB

I-65 SB & CD

I-65 SB

I-65 NB

ADMLS POINT DRIVE

38TH/ARLINGTON

US 31

I-65

AMERIPLEX PARKWAY

I-70 EB

I-74 WB EXIT RAMP

I-465 WB

GLENN ROAD

I-465

I-465 SB

WEST HANNA AVENUE

I-65 NB

86TH ST

DEAN RD

ALLISONVILLE RD

LAKESIDE DR

OAKLANDON RD

63RD STREET

MICHIGAN ROAD

CENTRAL AVE

GERMAN CHURCH ROAD

BURDSAL PKWY

COSSELL RD

ILLINOIS STREET

21ST ST

FRANKLIN ROAD

16TH ST

BRADBURY AVE

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