National Bridge Inventory: Montana



  • Of the 5,265 bridges in the state, 390, 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 284 bridges classified as structurally deficient in 2014.
  • 34 of the structurally deficient bridges are on the Interstate Highway System.
  • 340 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 1,041 bridges at an estimated cost of $535.9 million.
  • This compares to 952 bridges that needed work in 2014.

County Year Built Daily Crossings Type of Bridge Location
Missoula 1957 23,080 Urban other principal arterial N Russell St over Clark Fork River
Lewis and Clark 1978 17,288 Rural arterial US 12 over RR
Missoula 1962 14,039 Urban minor arterial S Higgins Ave over Clark Fork R-Ped Paths
Flathead 1975 13,173 Rural arterial S 40 over Whitefish River
Missoula 1966 9,489 Urban Interstate I 90 over Int Reserve Street
Granite 1970 9,241 Rural Interstate I 90 over Sep Bearmouth Road
Granite 1970 9,241 Rural Interstate I 90 over Clark Fork River
Hill 1976 9,135 Rural major collector S 234 over Scotts Coulee
Missoula 1964 8,315 Rural Interstate I 90 over Clark Fork River
Lewis and Clark 1962 8,157 Rural major collector Lincoln Rd over Int Lincoln-I 15
Flathead 1938 7,911 Rural arterial IRR - US 2 over S Fork Flathead River
Lake 1933 7,779 Rural arterial IRR - US 93 over Nine Pipe Reservoir
Gallatin 1972 7,399 Rural major collector Lone Mountain Trl over W Fork W Gallatin 1
Mineral 1980 6,882 Rural Interstate I 90 over Int Henderson
Mineral 1983 6,290 Rural Interstate I 90 over St. Regis Rvr-Int Ramp
Flathead 1955 6,179 Rural minor arterial S 82 over Flathead River
Missoula 1963 5,996 Rural Interstate I 90 over RR
Missoula 1963 5,996 Rural Interstate I 90 over RR
Missoula 1963 5,996 Rural Interstate I 90 over Sep E Mullan Road
Stillwater 1957 4,986 Rural minor arterial S 78 over Yellowstone River
Deer Lodge 1978 4,756 Rural Interstate I 90 over Int Warm Springs
Silver Bow 1963 4,591 Urban Interstate I 90 over Int I 15
Silver Bow 1963 4,591 Urban Interstate I 90 over Int I-15
Powell 1973 4,510 Rural Interstate I 90 over RR
Powell 1973 4,510 Rural Interstate I 90 over RR
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 745 600,818 2,946,940 30 61,158 127,563
Rural arterial 478 267,245 1,574,302 17 12,515 66,711
Rural minor arterial 509 223,567 536,189 34 29,416 43,261
Rural major collector 583 213,337 504,465 21 10,106 39,355
Rural minor collector 502 112,014 137,651 31 7,603 7,640
Rural local road 2,158 394,637 276,575 247 28,720 19,163
Urban Interstate 84 77,746 824,670 4 2,650 21,246
Urban freeway/expressway 0 0 0 0 0 0
Urban other principal arterial 58 120,757 844,735 1 1,331 23,080
Urban minor arterial 44 41,715 306,328 2 7,334 15,766
Urban collector 34 17,936 81,876 1 287 1,298
Urban local road 70 15,034 101,161 2 214 200
Total 5,265 2,084,807 8,134,892 390 161,334 365,283
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 589 $442 1,056,646 282,816
Widening & rehabilitation 4 $0 205 474
Rehabilitation 392 $93 378,075 163,610
Deck rehabilitation/replacement 5 $0 259 230
Other structural work 51 $1 15,468 13,267
Total 1,041 $536 1,450,653 460,397

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.

24
from 24 in 2017

in the nation in % of structurally deficient bridges

1. Rhode Island 23.1%
23. New Jersey 8.1%
24. Montana 7.4%
25. Wisconsin 7.4%

33
from 32 in 2017

in the nation in # of structurally deficient bridges

1. Iowa 4,675
32. Oregon 422
33. Montana 390
34. Washington 382
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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