National Bridge Inventory: Montana



  • Of the 5,278 bridges in the state, 367, or 7.0 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is down from 390 bridges classified as structurally deficient in 2018.
  • The deck area of structurally deficient bridges accounts for 6.5 percent of total deck area on all structures.
  • 20 of the structurally deficient bridges are on the Interstate Highway System. A total of 88.0 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.
  • 576 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 962 bridges at an estimated cost of $904.3 million.
  • This compares to 1,041 bridges that needed work in 2018.

County Year Built Daily Crossings Type of Bridge Location
Missoula 1966 23,428 Urban Interstate I 90 over Int Reserve Street
Yellowstone 1960 14,725 Urban other principal arterial Montana Ave over U1024-25-RR
Yellowstone 1960 14,725 Urban other principal arterial Montana Ave over U1025-RR
Missoula 1962 14,463 Urban minor arterial S Higgins Ave over Clark Fork R-Ped Paths
Granite 1970 11,516 Rural Interstate I 90 over Sep Bearmouth Road
Granite 1970 11,516 Rural Interstate I 90 over Clark Fork River
Missoula 1963 10,935 Rural Interstate I 90 over RR
Missoula 1963 10,935 Rural Interstate I 90 over RR
Deer Lodge 1978 8,817 Rural Interstate I 90 over Int Warm Springs
Flathead 1955 8,274 Rural minor arterial S 82 over Flathead River
Park 1979 8,206 Rural Interstate I 90 over Quinn Creek Rd
Park 1979 8,206 Rural Interstate I 90 over Quinn Creek Rd
Powell 1973 7,940 Rural Interstate I 90 over RR
Powell 1973 7,940 Rural Interstate I 90 over RR
Missoula 1964 7,090 Rural Interstate I 90 over Clark Fork River
Missoula 1979 7,090 Rural Interstate I 90 over Clark Fork River
Lake 1933 7,082 Rural arterial IRR - US 93 over Nine Pipe Reservoir
Lewis and Clark 1962 6,847 Rural major collector Lincoln Rd over Int Lincoln-I 15
Mineral 1984 6,498 Rural Interstate I 90 over Clark Fork River
Mineral 1965 6,410 Rural Interstate I 90 over Sep Elizabeth Ln
Mineral 1965 6,410 Rural Interstate I 90 over RR
Mineral 1965 6,410 Rural Interstate I 90 over Int Cyr-Clark Fork Rvr
Lincoln 1976 5,548 Rural arterial US 2 over Big Cherry Creek
Stillwater 1957 4,367 Rural minor arterial S 78 over Yellowstone River
Lewis and Clark 1966 3,997 Rural Interstate I 15 over Int Wolf Creek
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 743 598,597 5,205,599 19 30,008 136,643
Rural arterial 480 278,348 1,600,134 22 10,360 47,764
Rural minor arterial 498 224,888 507,701 44 28,605 46,818
Rural major collector 577 214,204 439,417 32 12,342 24,913
Rural minor collector 511 114,416 128,244 31 4,865 8,462
Rural local road 2,173 365,773 246,315 210 30,348 19,514
Urban Interstate 86 82,261 1,346,198 1 724 23,428
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 58 118,026 917,890 2 10,122 29,450
Urban minor arterial 45 48,021 344,696 2 7,334 16,447
Urban collector 35 17,988 90,040 2 394 2,931
Urban local road 72 16,969 86,507 2 213 200
Total 5,278 2,079,492 10,912,741 367 135,317 356,570
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 530 $648 1,425,601 265,057
Widening & rehabilitation 4 $1 205 475
Rehabilitation 367 $232 434,272 138,000
Deck rehabilitation/replacement 7 $1 339 381
Other structural work 54 $23 13,887 13,166
Total 962 $904 1,874,304 417,079

About the data:

Data and cost estimates are from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on February 1, 2023. 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 2021 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.

20
Compared to 24 in 2021

in the nation in % of structurally deficient bridges

1. West Virginia 20.0%
19. Kentucky 7.0%
20. Montana 7.0%
21. North Carolina 7.0%

34
Compared to 34 in 2021

in the nation in # of structurally deficient bridges

1. Iowa 4,604
33. Oregon 396
34. Montana 367
35. Maine 355

19
Compared to 16 in 2021

in the nation in % of structurally deficient bridge deck area

1. Rhode Island 17.0%
18. Alaska 7.0%
19. Montana 7.0%
20. New Hampshire 7.0%
Full State Ranking

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  • Source: Data is from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on February 1, 2023. Note that specific conditions on bridges may have changed as a result of recent work or updated inspections.

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