National Bridge Inventory: Iowa

  • Of the 23,982 bridges in the state, 4,571, or 19.1 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is down from 4,671 bridges classified as structurally deficient in 2016.
  • The deck area of structurally deficient bridges accounts for 10.0 percent of total deck area on all structures.
  • 6 of the structurally deficient bridges are on the Interstate Highway System. A total of 99.5 percent of the structurally deficient bridges are not on the National Highway System, which includes the Interstate and other key roads linking major airports, ports, rail and truck terminals.
  • 5,416 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 15,308 bridges at an estimated cost of $3.1 billion.
  • This compares to 15,178 bridges that needed work in 2016.

County Year Built Daily Crossings Type of Bridge Location
Scott 1940 30,400 Urban other principal arterial Centennial Bridge
Scott 1970 25,100 Urban Interstate I-280 over Mississippi River & Road
Scott 1963 20,000 Urban minor arterial N Division St over Duck Creek
Polk 1936 18,600 Urban minor arterial 2nd Ave over Birdland Dr
Polk 1967 17,600 Urban minor arterial Sw 9th St over Cherry, RR, Mlk Pkwy
Scott 1900 16,700 Urban minor arterial Eastern Ave over Duck Creek
Woodbury 1962 14,550 Urban Interstate I-29 over Channel Floyd River
Johnson 1972 14,500 Urban minor arterial Gilbert St over Ralston Creek
Woodbury 2017 13,450 Urban Interstate I 29 NB over Perry Creek Conduit
Poweshiek 1963 13,250 Rural Interstate I 80 WB over Iowa 21
Poweshiek 1962 12,900 Urban Interstate WB I 80 over Iowa 146
Poweshiek 1962 12,900 Urban Interstate EB I 80 over Iowa 146
Marshall 1951 11,100 Urban minor arterial So Center St over RR and Madison St
Polk 1958 10,800 Urban minor arterial Se 30th St over UP RR
Johnson 1915 10,650 Urban other principal arterial Ia 1 NB over Iowa River
Webster 1968 10,300 Urban minor arterial 1St Ave S over 21St St & RR
Linn 1938 10,050 Urban other principal arterial 8th Ave over Cedar River
Woodbury 1962 9,900 Urban minor arterial Dace Ave over Floyd River
Scott 1895 9,900 Urban minor arterial Fort Rd & RR over Mississippi River
Black Hawk 1950 9,800 Urban minor arterial E Ridgeway Ave over Dry Run Creek
Woodbury 1962 9,500 Urban minor arterial 6th St over Floyd River
Webster 1955 9,300 Urban other principal arterial 5th Ave over drainage Ditch
Plymouth 1948 8,300 Rural arterial SB US 75 over Stream
Woodbury 1976 8,000 Urban minor arterial Military Rd over Big Sioux River
Black Hawk 1953 7,400 Urban minor arterial E 11th St over Cedar River
Type of Bridge Number of Bridges Area of All Bridges
(sq. meters)
Daily Crossings on All Bridges Number of Structurally Deficient Bridges Area of Structurally Deficient Bridges
(sq. meters)
Daily Crossings on Structurally Deficient Bridges
Rural Interstate 373 333,168 4,900,460 1 648 13,250
Rural arterial 1,261 1,067,030 5,595,175 9 4,500 43,330
Rural minor arterial 1,076 610,204 2,051,540 18 13,164 32,530
Rural major collector 3,447 1,266,262 2,591,408 590 189,383 397,590
Rural minor collector 3,882 995,049 552,265 724 137,037 85,295
Rural local road 11,600 1,823,063 621,457 3,066 337,776 129,402
Urban Interstate 352 706,919 8,375,605 5 39,076 78,900
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 628 1,105,636 5,641,410 4 23,327 60,400
Urban minor arterial 544 615,387 3,502,697 45 69,960 296,635
Urban collector 316 194,955 837,740 31 17,576 56,250
Urban local road 503 179,727 459,216 78 42,292 42,501
Total 23,982 8,897,400 35,128,973 4,571 874,738 1,236,083
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 7,237 $1,421 1,584,089 1,267,080
Widening & rehabilitation 67 $28 119,429 36,553
Rehabilitation 1,236 $342 927,467 443,700
Deck rehabilitation/replacement 45 $17 50,895 22,191
Other structural work 6,723 $1,326 2,778,033 1,740,695
Total 15,308 $3,134 5,459,913 3,510,219

About the data:

Data is from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on March 11, 2021. Note that specific conditions on bridges may have changed as a result of recent work or updated inspections. Cost estimates were downloaded by ARTBA on March 11, 2021.

Effective January 1, 2018, FHWA changed the definition of structurally deficient as part of the final rule on highway and bridge performance measures, published May 20, 2017 pursuant to the 2012 federal aid highway bill Moving Ahead for Progress in the 21st Century Act (MAP-21). Two measures that were previously used to classify bridges as structurally deficient are no longer used. This includes bridges where the overall structural evaluation was rated in poor or worse condition, or where the adequacy of waterway openings was insufficient.

The new definition limits the classification to bridges where one of the key structural elements—the deck, superstructure, substructure or culverts, are rated in poor or worse condition. During inspection, the conditions of a variety of bridge elements are rated on a scale of 0 (failed condition) to 9 (excellent condition). A rating of 4 is considered “poor” condition.

Cost estimates have been derived by ARTBA, based on 2019 average bridge replacement costs for structures on and off the National Highway System, published by FHWA. Bridge rehabilitation costs are estimated to be 68 percent of replacement costs. A bridge is considered to need repair if the structure has identified repairs as part of the NBI, a repair cost estimate is supplied by the bridge owner or the bridge is classified as structurally deficient. Please note that for a few states, the number of bridges needing to be repaired can vary significantly from year to year, and reflects the data entered by the state.

Bridges are classified by FHWA into types based on the functional classification of the roadway on the bridge. Interstates comprise routes officially designated by the Secretary of Transportation. Other principal arterials serve major centers of urban areas or provide mobility through rural areas. Freeways and expressways have directional lanes generally separated by a physical barrier, and access/egress points generally limited to on- and off-ramps. Minor arterials serve smaller areas and are used for trips of moderate length. Collectors funnel traffic from local roads to the arterial network; major collectors have higher speed limits and traffic volumes and are longer in length and spaced at greater intervals, while minor collectors are shorter and provide service to smaller communities. Local roads do not carry through traffic and are intended for short distance travel.

Compared to 3 in 2019

in the nation in % of structurally deficient bridges

1. West Virginia 21.2%
2. Iowa 19.1%
3. Rhode Island 19.0%

Compared to 1 in 2019

in the nation in # of structurally deficient bridges

1. Iowa 4,571
2. Pennsylvania 3,353

Compared to 7 in 2019

in the nation in % of structurally deficient bridge deck area

1. Rhode Island 21.0%
5. Iowa 10.0%
6. South Dakota 10.0%
Full State Ranking


  • Source: Data is from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on March 11, 2021. Note that specific conditions on bridges may have changed as a result of recent work or updated inspections.

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