National Bridge Inventory: Montana



  • The state has identified needed repairs on 938 bridges.
  • This compares to 971 bridges that needed work in 2021.
  • Over the life of the IIJA, Montana will receive a total of $225.0 million in bridge formula funds, which will help make needed repairs.
  • Montana currently has access to $180.0 million of that total, and has committed $136.7 million towards 43 projects as of June 2025.
  • Of the 5,235 bridges in the state, 388, or 7.4 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is up from 365 bridges classified as structurally deficient in 2021.
  • The deck area of structurally deficient bridges accounts for 6.1 percent of total deck area on all structures.

Top Most Traveled Structurally Deficient Bridges in Montana

County Year Built Daily Crossings Type of Bridge Location
Missoula 1966 13,664 Urban Interstate I 90 over Int Reserve Street
Granite 1970 13,081 Rural Interstate I 90 over Clark Fork River
Missoula 1964 9,168 Rural Interstate I 90 over Clark Fork River
Yellowstone 1960 8,576 Urban other principal arterial Montana Ave over U1025-RR
Yellowstone 1960 8,576 Urban other principal arterial Montana Ave over U1024-25-RR
Gallatin 1969 8,575 Rural Interstate I 90 over Abandoned RR
Flathead 1955 8,310 Rural minor arterial S 82 over Flathead River
Lake 1933 8,158 Rural arterial IRR - US 93 over Nine Pipe Reservoir
Lewis and Clark 1962 7,492 Rural minor arterial Lincoln Rd over Int Lincoln-I 15
Powell 1973 5,992 Rural Interstate I 90 over RR
Powell 1973 5,992 Rural Interstate I 90 EB over RR
Lincoln 1976 5,295 Rural arterial US 2 over Big Cherry Creek
Powell 1979 5,232 Rural Interstate I 90 over Int W Garrison-RR
Stillwater 1957 5,017 Rural minor arterial S 78 over Yellowstone River
Dawson 1973 4,317 Rural Interstate I 94 over Clear Creek
Madison 1934 4,102 Rural minor arterial US 287 over South Willow Creek
Mineral 1965 4,088 Rural Interstate I 90 over Clark Fork River
Mineral 1965 4,088 Rural Interstate I 90 over Sep Elizabeth Ln
Yellowstone 1949 4,005 Rural minor arterial Old Hwy 312 over Yellowstone River 170
Mineral 1984 3,719 Rural Interstate I 90 over Clark Fork River
Blaine 1964 3,311 Rural arterial IRR - US 2 over Milk River
Yellowstone 1959 3,188 Urban minor arterial S Shiloh Rd over Sep I 90
Park 1962 2,910 Rural arterial US 89 over Int East Livingston I 90
Richland 1957 2,821 Rural arterial S 16 over Crane Creek
Beaverhead 1946 2,676 Rural major collector Hwy 91 N over Beaverhead River 033

Bridge Inventory: Montana

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 689 542,193 2,827,241 13 22,979 67,986
Rural arterial 449 233,633 1,454,563 31 13,758 62,821
Rural minor arterial 474 227,295 540,134 45 30,551 63,067
Rural major collector 634 225,138 364,826 43 12,092 24,384
Rural minor collector 552 122,071 116,485 34 5,219 6,526
Rural local road 1,974 322,416 214,217 207 28,084 19,838
Urban Interstate 138 140,033 1,222,860 1 724 13,664
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 86 168,259 1,158,633 2 10,122 17,152
Urban minor arterial 64 48,290 434,061 2 2,081 3,288
Urban collector 80 32,672 192,347 5 1,812 7,641
Urban local road 95 34,651 65,281 5 674 500
Total 5,235 2,096,651 8,590,648 388 128,096 286,867

Proposed Bridge Work

Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 502 $855 1,028,108 261,995
Widening & rehabilitation 4 $1 205 475
Rehabilitation 376 $302 369,027 137,198
Deck rehabilitation/replacement 6 $1 299 328
Other structural work 50 $29 14,619 13,324
Total 938 $1,187 1,412,258 413,320

About the data:

Data and cost estimates are from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on June 24, 2025. 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 2023 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 20 in 2024

in the nation in % of structurally deficient bridges

1. Iowa 19.0%
19. Kentucky 8.0%
20. Montana 7.0%
21. North Carolina 7.0%

34
Compared to 35 in 2024

in the nation in # of structurally deficient bridges

1. Iowa 4,424
33. New Jersey 392
34. Montana 388
35. Florida 360

16
Compared to 22 in 2024

in the nation in % of structurally deficient bridge deck area

1. West Virginia 13.0%
15. Connecticut 6.0%
16. Montana 6.0%
17. Louisiana 6.0%
Full State Ranking

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  • Source: Data is from the Federal Highway Administration (FHWA) National Bridge Inventory (NBI), downloaded on June 24, 2025. Note that specific conditions on bridges may have changed as a result of recent work or updated inspections.

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