National Bridge Inventory: Iowa



  • Of the 24,123 bridges in the state, 4,675, or 19.4 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is down from 4,691 bridges classified as structurally deficient in 2014.
  • 7 of the structurally deficient bridges are on the Interstate Highway System.
  • 4,815 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 15,350 bridges at an estimated cost of $1.6 billion.
  • This compares to 15,309 bridges that needed work in 2014.

County Year Built Daily Crossings Type of Bridge Location
Scott 1940 33,400 Urban other principal arterial Centennial Bridge
Scott 1970 25,900 Urban Interstate I-280 over Mississippi River & Road
Polk 1942 25,700 Urban other principal arterial IA 415 over NW 66th Ave
Woodbury 1959 23,700 Urban Interstate I29 SB Old Divi over Floyd Blvd
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
Woodbury 1962 14,550 Urban Interstate I-29 over Channel Floyd River
Johnson 1972 14,500 Urban minor arterial Gilbert St over Ralston Creek
Poweshiek 1963 13,650 Rural Interstate I 80 WB over Iowa 21
Johnson 1915 13,500 Urban other principal arterial Ia 1 NB over Iowa River
Poweshiek 1962 12,600 Urban Interstate EB I 80 over Iowa 146
Poweshiek 1962 12,500 Urban Interstate WB I 80 over Iowa 146
Webster 1955 11,200 Urban other principal arterial 5th Ave over drainage Ditch
Marshall 1951 11,100 Urban minor arterial So Center St over Linn Creek
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
Webster 1968 10,200 Urban minor arterial 1St Ave S over 21St St & RR
Linn 1938 10,050 Urban other principal arterial 8th Ave over Cedar River
Polk 1918 9,900 Urban minor arterial Court Ave over Des Moines 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
Johnson 1959 9,100 Urban minor arterial Park Rd over Iowa River
Polk 1918 8,200 Urban minor arterial Grand Ave over Des Moines River
Woodbury 1976 8,000 Urban minor arterial Military Rd over Big Sioux River
Plymouth 1948 7,950 Rural arterial SB US 75 over Small Natural Stream
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 371 287,290 4,724,725 1 648 13,650
Rural arterial 1,266 1,076,285 5,643,660 10 3,141 37,100
Rural minor arterial 1,075 605,800 2,087,290 24 16,021 43,610
Rural major collector 3,446 1,251,672 2,540,923 566 180,260 368,080
Rural minor collector 3,912 991,734 556,375 725 130,899 87,830
Rural local road 11,755 1,815,215 622,086 3,184 348,161 135,651
Urban Interstate 359 761,837 8,663,040 6 42,269 94,700
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 601 1,045,903 5,580,650 7 23,832 97,010
Urban minor arterial 544 622,573 3,540,608 50 89,936 296,515
Urban collector 308 185,853 793,675 28 15,728 45,460
Urban local road 486 162,745 441,657 74 38,068 39,211
Total 24,123 8,806,907 35,194,689 4,675 888,963 1,258,817
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 7,400 $1,364 1,533,843 1,252,359
Widening & rehabilitation 76 $3 125,474 38,224
Rehabilitation 1,417 $96 987,831 472,938
Deck rehabilitation/replacement 52 $4 61,150 27,030
Other structural work 6,405 $137 2,717,266 1,649,950
Total 15,350 $1,604 5,425,564 3,440,502

About the data:

Data from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), released March 15, 2019. Note that specific conditions on bridges may have changed as a result of recent work or updated inspections.

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 2017 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 cost estimate is supplied by the bridge owner or the bridge is classified as structurally deficient.

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.

3
from 2 in 2017

in the nation in % of structurally deficient bridges

1. Rhode Island 23.1%
3. Iowa 19.4%
4. South Dakota 16.7%

1
from 1 in 2017

in the nation in # of structurally deficient bridges

1. Iowa 4,675
2. Pennsylvania 3,770
Full State Ranking

  • Source: Bridge data is from the 2018 National Bridge Inventory ASCII files, released by the Federal Highway Administration on March 14, 2019. Note that specific conditions on bridges may have changed as a result of recent work. ARTBA is a non-partisan federation whose primary goal is to aggressively grow and protect transportation infrastructure investment to meet the public and business demand for safe and efficient travel.
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