National Bridge Inventory: Montana



  • Of the 5,271 bridges in the state, 377, or 7.2 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is up from 369 bridges classified as structurally deficient in 2016.
  • The deck area of structurally deficient bridges accounts for 7.3 percent of total deck area on all structures.
  • 28 of the structurally deficient bridges are on the Interstate Highway System. A total of 87.5 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.
  • 511 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 987 bridges at an estimated cost of $765.3 million.
  • This compares to 1,013 bridges that needed work in 2016.

County Year Built Daily Crossings Type of Bridge Location
Missoula 1957 21,372 Urban other principal arterial N Russell St over Clark Fork River
Missoula 1962 15,220 Urban minor arterial S Higgins Ave over Clark Fork R-Ped Paths
Yellowstone 1960 11,162 Urban other principal arterial Montana Ave over U1024-25-RR
Yellowstone 1960 11,162 Urban other principal arterial Montana Ave over U1025-RR
Hill 1976 10,796 Rural major collector S 234 over Scotts Coulee
Missoula 1966 10,155 Urban Interstate I 90 over Int Reserve Street
Granite 1970 9,578 Rural Interstate I 90 over Clark Fork River
Granite 1970 9,578 Rural Interstate I 90 over Sep Bearmouth Road
Gallatin 1979 8,521 Rural major collector Lone Mountain Trl over Middle Fk W Gallatin 4
Gallatin 1972 8,521 Rural major collector Lone Mountain Trl over W Fork W Gallatin 1
Flathead 1955 8,357 Rural minor arterial S 82 over Flathead River
Missoula 1964 8,086 Rural Interstate I 90 over Clark Fork River
Lewis and Clark 1962 7,910 Rural major collector Lincoln Rd over Int Lincoln-I 15
Park 1979 7,406 Rural Interstate I 90 over Quinn Creek Rd
Park 1979 7,406 Rural Interstate I 90 over Quinn Creek Rd
Lake 1933 7,209 Rural arterial IRR - US 93 over Nine Pipe Reservoir
Missoula 1963 6,000 Rural Interstate I 90 over Sep E Mullan Road
Missoula 1963 6,000 Rural Interstate I 90 over RR
Missoula 1963 6,000 Rural Interstate I 90 over RR
Cascade 1960 5,399 Rural arterial US 89 over Int Vaughn-I 15
Deer Lodge 1978 4,764 Rural Interstate I 90 over Int Warm Springs
Stillwater 1957 4,386 Rural minor arterial S 78 over Yellowstone River
Powell 1973 4,293 Rural Interstate I 90 over RR
Powell 1973 4,293 Rural Interstate I 90 over RR
Dawson 1973 4,091 Rural Interstate I 94 over Clear 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 742 600,805 3,013,658 26 45,064 117,336
Rural arterial 478 271,015 1,625,977 16 9,222 36,079
Rural minor arterial 501 223,498 530,212 41 28,884 47,891
Rural major collector 583 213,220 495,586 25 11,509 50,001
Rural minor collector 504 112,689 132,126 35 5,428 11,502
Rural local road 2,171 362,263 262,599 224 29,606 17,644
Urban Interstate 87 83,991 860,280 2 1,177 13,172
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 57 113,805 854,233 3 11,453 43,696
Urban minor arterial 45 48,667 332,031 2 7,334 17,277
Urban collector 34 17,881 82,901 1 288 1,307
Urban local road 69 15,055 110,125 2 213 200
Total 5,271 2,062,890 8,299,728 377 150,178 356,105
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 559 $537 1,032,169 272,826
Widening & rehabilitation 4 $1 205 475
Rehabilitation 362 $202 358,891 145,686
Deck rehabilitation/replacement 6 $0 314 330
Other structural work 56 $25 22,216 17,125
Total 987 $765 1,413,795 436,442

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.

25
Compared to 24 in 2019

in the nation in % of structurally deficient bridges

1. West Virginia 21.2%
24. Kentucky 7.2%
25. Montana 7.2%
26. Wyoming 7.0%

34
Compared to 33 in 2019

in the nation in # of structurally deficient bridges

1. Iowa 4,571
33. Oregon 395
34. Montana 377
35. Georgia 374

17
Compared to 18 in 2019

in the nation in % of structurally deficient bridge deck area

1. Rhode Island 21.0%
16. Connecticut 8.0%
17. Montana 7.0%
18. Alaska 7.0%
Full State Ranking

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  • 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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