County profile · official public datasets

Polk County, IA

545 public highway bridges tracked in the FHWA National Bridge Inventory: 57.8% rated Good, 35.8% Fair, 6.4% Poor.

545
Public bridges
57.8%
Good condition
6.4%
Poor condition

The verdict

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

Polk County pairs a top-10% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 7%
lowest Poor share in state
6.4%
Poor-condition share
545
public highway bridges
1986
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.

Polk County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Polk County ranks #7 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.4%). Polk County, Iowa contains 545 public highway bridges. Roughly 57.8% are rated “Good,” 35.8% “Fair,” and 6.4% “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

545

Public highway bridges in Polk County

Good condition

57.8%

315 of 545 rated 7-9

Fair condition

35.8%

195 of 545 rated 5-6

Poor condition

6.4%

35 of 545 rated 4 or below

In-state Poor-share rank

#7 of 99

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

Condition distribution

Share of 545 NBI-tracked bridges by lowest applicable component rating.

Good
57.8% (315)
Fair
35.8% (195)
Poor
6.4% (35)

Polk County's Poor-condition bridges carry 81,796 vehicle crossings a day

That is 1.2% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,406 crossings a day against 11,988 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 542 of 545 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

29.9% of Polk County's bridges have passed the 50-year mark

163 of the 545 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 57.8% 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 19.1% of the county's Poor-condition bridge traffic

FLEUR DR over OLD UP RR & SW 22ND, built 1936, carries 15,634 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 35-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 81,796 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Polk County's bridges were built

545 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 2000s, when 142 of the county's bridges still in the inventory were built, which is 26.1% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1986, 7 years newer than the Iowa average of 1979.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

How Polk County compares with Iowa's closest counties by inventory size

The 5 Iowa counties nearest Polk County in number of bridges, with their condition splits. Its 6.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1986 against a peer-group mean of 1984 is in line with the group.

Showing the 5 closest of 98 Iowa counties eligible for comparison.

Bridge inventory size and condition shares for Polk County and the 5 Iowa counties closest to it in inventory size
County Bridges Poor
Pottawattamie County 557 9.3%
Polk County (this page) 545 6.4%
Linn County 506 6.3%
Black Hawk County 489 6.5%
Woodbury County 455 21.1%
Sioux County 449 2.9%

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

Similar inventory size

Nearest county inventories outside IA (545 bridges here).

Similar average build year

Nearest mean year-built outside IA (1986 here).

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

All 545 Good 315 Fair 195 Poor 35

Good-condition bridges (315)

LOCAL ROAD

Good

Over: DRAINAGE DITCH

081232307, Polk, IA

Built 2000 Load: 32.7 t ADT: 11

LOCAL ROAD

Good

Over: OLD SKUNK R CHAN

081232401, Polk, IA

Built 1992 Load: 32.7 t ADT: 5

39TH ST

Good

Over: JORDAN CREEK

000000000, Polk, IA

Built 1974 Load: 32.7 t ADT: 2,565

50TH ST

Good

Over: JORDAN CREEK

000000000, Polk, IA

Built 2005 Load: 32.7 t ADT: 8,476

NETRILEIN DR

Good

Over: BR.FOUR MILE CREEK

080241300, Polk, IA

Built 1991 Load: 32.7 t ADT: 1,404

LINCOLN ST.

Good

Over: DRAINAGE DITCH

080223100, Polk, IA

Built 1996 Load: 32.7 t ADT: 1,190

US 6

Good

Over: I-235

At Jct. I-235, Polk, IA

Built 2003 Load: 32.7 t ADT: 21,400

NW 18TH STREET

Good

Over: ROCK CREEK

080241001, Polk, IA

Built 2003 Load: 32.7 t ADT: 5,613

SW STATE STREET

Good

Over: SAYLOR CREEK

080242700, Polk, IA

Built 1997 Load: 32.7 t ADT: 748

MLK JR PKWY E/W

Good

Over: RACCOON RIVER

078240801, Polk, IA

Built 2005 Load: 32.7 t ADT: 7,253

LITTLE 4 MI CRK DR

Good

Over: E FOUR MILE CREEK

078230400, Polk, IA

Built 2004 Load: 32.7 t ADT: 2,740

NORTH JAMES ST

Good

Over: TRIB LITTLE BEAVER CREEK

080253200, Polk, IA

Built 2006 Load: 32.7 t ADT: 5,988

N PARK ST

Good

Over: LITTLE BEAVER CREEK

080252900, Polk, IA

Built 2007 Load: 32.7 t ADT: 288

SE 9TH ST

Good

Over: CRAWFORD CREEK

078241000, Polk, IA

Built 2010 Load: 32.7 t ADT: 465

E OVID AVENUE

Good

Over: 7TH WARD DITCH

079233000, Polk, IA

Built 1996 Load: 32.7 t ADT: 1,823

SW MAGAZINE RD

Good

Over: SAYLOR CREEK

080242701, Polk, IA

Built 2008 Load: 32.7 t ADT: 89

SW PRAIRIE TRL

Good

Over: SAYLOR CREEK

080242600, Polk, IA

Built 2013 Load: 32.7 t ADT: 344

N MAIN ST

Good

Over: CREEK

080253200, Polk, IA

Built 2002 Load: 32.7 t ADT: 143

64TH ST

Good

Over: DRAINAGE

T78N R26W S13 DAL CO, Polk, IA

Built 2009 Load: 32.7 t ADT: 43

IA 5 NB

Good

Over: IA 28

At Jct. IA 28, Polk, IA

Built 2000 Load: 32.7 t ADT: 10,900

MAFFITT LAKE RD

Good

Over: I-35

0.2 mi. S of Jct. IA 5, Polk, IA

Built 2000 Load: 32.7 t ADT: 1,572

IA 5 RAMP C NB

Good

Over: DRAINAGE

1.0 MILE S OF I-35 JUNCT, Polk, IA

Built 2000 Load: 32.7 t ADT: 1,220

IA 5 NB

Good

Over: 8TH STREET

1.6 MILES NW JCT IA 28, Polk, IA

Built 2002 Load: 32.7 t ADT: 15,050

I 35 NB

Good

Over: OVER UP RR

1.1 MILES N OF N JCT I-80, Polk, IA

Built 2002 Load: 32.7 t ADT: 45,700

E UNIVERSITY

Good

Over: SMALL CREEK

078230600, Polk, IA

Built 2003 Load: 32.7 t ADT: 27,200

IA 141 FLY OVER

Good

Over: I 35/80 IA 141 & RR

AT JCT. IA 141 & I-35/80, Polk, IA

Built 2019 Load: 32.7 t ADT: 15,100

7TH ST

Good

Over: I-235/3RD ST. RAMP B

1.5 mi. W of US 69, Polk, IA

Built 2003 Load: 32.8 t ADT: 6,200

US 65 NB

Good

Over: NE 27TH AVE & BIKE PATH

3.3 MILES S OF JCT I-80, Polk, IA

Built 1994 Load: 32.8 t ADT: 14,300

US 65 SB

Good

Over: NE 27TH AVE & BIKE PATH

3.3 MILES S OF JCT I-80, Polk, IA

Built 1994 Load: 32.8 t ADT: 14,300

CHAYSE ST SW

Good

Over: DITCH NUMBER 2

080233600, Polk, IA

Built 2021 Load: 33.0 t ADT: 14

56TH ST

Good

Over: I-235

0.5 mi. E of Jct. IA 28, Polk, IA

Built 2005 Load: 33.1 t ADT: 5,745

SB US 65

Good

Over: OVER UP RR

1.9 MILES N OF N JCT IA 5, Polk, IA

Built 1997 Load: 33.1 t ADT: 12,450

WBI80 TO WBI235

Good

Over: NB I-35 & EB I-80

At NE Mix Master in D.M., Polk, IA

Built 2009 Load: 33.1 t ADT: 4,500

2ND AVE ON RAMP

Good

Over: S-W CONN OVER WB I-235

4.4 MILES E OF JCT IA 28, Polk, IA

Built 2002 Load: 33.2 t ADT: 8,500

2ND AVE

Good

Over: I-235

4.4 MILES E OF JCT IA 28, Polk, IA

Built 2003 Load: 33.2 t ADT: 8,400

EB IA 141

Good

Over: IA 17

AT JUNCTION IOWA 17, Polk, IA

Built 1974 Load: 33.2 t ADT: 5,600

WB IA 141

Good

Over: IA 17

AT JUNCTION IOWA 17, Polk, IA

Built 1974 Load: 33.2 t ADT: 5,600

NB I-35 EB I-80

Good

Over: NE 3RD ST

0.3 mi. E of Jct. IA 415, Polk, IA

Built 2000 Load: 33.3 t ADT: 39,550

SB I-35 WB I-80

Good

Over: NE 3RD ST

0.3 mi. E of Jct. 415, Polk, IA

Built 2000 Load: 33.3 t ADT: 39,550

60TH ST

Good

Over: JORDON CREEK

P60800590, Polk, IA

Built 1992 Load: 33.3 t ADT: 13,750

IA 415

Good

Over: DRAINAGE DITCH

0.5 MI. S OF JCT. IA 160, Polk, IA

Built 1983 Load: 33.7 t ADT: 27,000

SB US 65

Good

Over: SE 38TH ST

0.8 MILE S OF N JCT IA 5, Polk, IA

Built 1997 Load: 33.9 t ADT: 10,900

NE 3RD ST

Good

Over: CREEK

0.13 Mi. N. of NE 6 Ave., Polk, IA

Built 2020 Load: 34.0 t ADT: 2,521

NE 118TH AVE

Good

Over: BRANCH SKUNK RIVER

080220301, Polk, IA

Built 2000 Load: 34.0 t ADT: 45

NW 134TH AVE

Good

Over: FOUR MILE CREEK

0.2 mi E of NW 2nd St, Polk, IA

Built 2021 Load: 34.0 t ADT: 180

142ND ST

Good

Over: WALNUT CREEK

O57000543, Polk, IA

Built 2006 Load: 34.0 t ADT: 3,538

WB I-235

Good

Over: 73RD ST& IA Interstate R

3.2 MI E OF W JCT I 80/35, Polk, IA

Built 1968 Load: 34.3 t ADT: 54,350

NE 102ND AVE

Good

Over: DRAINAGE DITCH NO 38

080221401, Polk, IA

Built 2016 Load: 34.3 t ADT: 459

NE SANTIAGO DR

Good

Over: CREEK

080222111, Polk, IA

Built 2017 Load: 34.3 t ADT: 300

LOCAL RD

Good

Over: FOUR MILE CREEK

080231800, Polk, IA

Built 1991 Load: 34.3 t ADT: 7,530

Read our methodology - how this data is sourced, computed, and verified.

Related

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Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges

Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.