National Bridge Inventory: New Hampshire



  • Of the 2,531 bridges in the state, 190, or 7.5 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is down from 224 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.
  • 11 of the structurally deficient bridges are on the Interstate Highway System. A total of 86.3 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.
  • 136 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 2,476 bridges at an estimated cost of $5.1 billion.
  • This compares to 2,444 bridges that needed work in 2018.

County Year Built Daily Crossings Type of Bridge Location
Merrimack 1959 41,631 Urban Interstate I-89 over South Street
Merrimack 1958 39,406 Urban Interstate I-393,US 4,US202 over I-93
Merrimack 1958 39,406 Urban minor arterial US202 over NHRR,Constitution Av.
Merrimack 1980 35,458 Urban Interstate I-393,US 4,US202 over Fort Eddy Rd
Merrimack 1966 21,649 Urban minor arterial Nh 9(Loudon Road) over Merrimack River
Hillsborough 1923 20,952 Urban other principal arterial US 3,NH 3A over I-293,NH 3A,PAR,Merr R
Hillsborough 1956 20,848 Urban Interstate I-293,NH 3A,Tpk N over Black Brook
Grafton 1966 20,502 Urban Interstate I-89 NB over US 4,NH 10
Strafford 1957 20,420 Urban freeway/expressway Nh 16,Sp Tpk SB over Cocheco River
Grafton 1966 20,105 Urban Interstate I-89 NB over Connecticut River,Necrr
Strafford 1957 19,515 Urban freeway/expressway Nh 16,Sp Tpk NB over Cocheco River
Grafton 1966 19,185 Urban Interstate I-89 SB over Connecticut River,Necrr
Strafford 1957 19,171 Urban freeway/expressway Nh 16,Sp Tpk NB over Nh108,Par(Abd)
Hillsborough 1956 19,034 Urban Interstate I-293,NH 3A,Tpk S over Black Brook
Strafford 1957 18,289 Urban freeway/expressway Nh 16,Sp Tpk SB over Nh108,Par(Abd)
Hillsborough 1958 16,350 Rural arterial US202,Nh101 over Contoocook River
Merrimack 1959 16,159 Rural Interstate I-89 SB over Turkey Pond
Merrimack 1959 15,954 Rural Interstate I-89 NB over Turkey Pond
Hillsborough 1928 14,357 Urban other principal arterial Canal Street over Nashua River
Rockingham 1936 14,258 Urban other principal arterial US 1 over Par(Abd)
Rockingham 1935 13,985 Urban other principal arterial US 1 over Par
Hillsborough 1933 13,016 Urban minor arterial US 3 over Baboosic Brook
Belknap 1962 12,484 Rural Interstate I-93 NB over Salmon Brook
Hillsborough 1931 12,480 Urban minor arterial Nh 13 over Souhegan River
Strafford 1951 12,442 Urban other principal arterial Nh125 over Isinglass River
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 208 119,494 1,810,400 3 2,646 44,597
Rural arterial 124 57,294 1,008,854 4 1,289 36,070
Rural minor arterial 165 61,138 715,749 9 2,576 40,591
Rural major collector 199 67,166 501,310 21 9,546 44,823
Rural minor collector 182 37,204 223,977 11 3,891 10,469
Rural local road 862 112,918 271,422 87 9,765 35,050
Urban Interstate 163 209,994 4,470,564 8 9,465 216,169
Urban freeway/expressway 92 118,986 2,475,599 4 4,431 77,395
Urban other principal arterial 112 164,755 1,621,571 7 11,897 96,546
Urban minor arterial 134 104,124 1,305,444 13 12,918 156,801
Urban collector 118 58,021 562,025 9 4,924 46,022
Urban local road 172 48,083 240,077 14 1,793 14,250
Total 2,531 1,159,177 15,206,992 190 75,141 818,783
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 2,464 $5,112 15,192,281 1,153,202
Widening & rehabilitation 0 $0 0 0
Rehabilitation 8 $3 394 791
Deck rehabilitation/replacement 1 $1 50 180
Other structural work 3 $8 11,001 2,174
Total 2,476 $5,124 15,203,726 1,156,348

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.

18
Compared to 18 in 2021

in the nation in % of structurally deficient bridges

1. West Virginia 20.0%
17. Alaska 8.0%
18. New Hampshire 8.0%
19. Kentucky 7.0%

43
Compared to 43 in 2021

in the nation in # of structurally deficient bridges

1. Iowa 4,604
42. New Mexico 199
43. New Hampshire 190
44. Rhode Island 130

20
Compared to 19 in 2021

in the nation in % of structurally deficient bridge deck area

1. Rhode Island 17.0%
19. Montana 7.0%
20. New Hampshire 7.0%
21. California 6.0%
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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