National Bridge Inventory: New Hampshire



  • Of the 2,514 bridges in the state, 215, or 8.6 percent, are classified as structurally deficient. This means one of the key elements is in poor or worse condition.
  • This is down from 249 bridges classified as structurally deficient in 2016.
  • The deck area of structurally deficient bridges accounts for 6.8 percent of total deck area on all structures.
  • 9 of the structurally deficient bridges are on the Interstate Highway System. A total of 85.6 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.
  • 147 bridges are posted for load, which may restrict the size and weight of vehicles crossing the structure.
  • The state has identified needed repairs on 2,462 bridges at an estimated cost of $6.0 billion.
  • This compares to 2,444 bridges that needed work in 2016.

County Year Built Daily Crossings Type of Bridge Location
Merrimack 1959 48,774 Urban Interstate I-89 over South Street
Merrimack 1958 46,136 Urban Interstate I-393,US 4,US202 over I-93
Merrimack 1958 46,136 Urban minor arterial US202 over NHRR,Constitution Av.
Merrimack 1980 44,015 Urban Interstate I-393,US 4,US202 over Fort Eddy Rd
Merrimack 1966 25,347 Urban minor arterial Nh 9(Loudon Road) over Merrimack River
Strafford 1957 24,688 Urban freeway/expressway Nh 16,Sp Tpk NB over Cocheco River
Hillsborough 1923 24,531 Urban other principal arterial US 3,NH 3A over I-293,NH 3A,PAR,Merr R
Hillsborough 1956 24,408 Urban Interstate I-293,NH 3A,Tpk N over Black Brook
Strafford 1957 23,907 Urban freeway/expressway Nh 16,Sp Tpk SB over Cocheco River
Strafford 1957 23,012 Urban freeway/expressway Nh 16,Sp Tpk NB over Nh108,Par(Abd)
Grafton 1966 22,596 Urban Interstate I-89 NB over US 4,NH 10
Hillsborough 1956 22,285 Urban Interstate I-293,NH 3A,Tpk S over Black Brook
Strafford 1957 21,551 Urban freeway/expressway Nh 16,Sp Tpk SB over Nh108,Par(Abd)
Grafton 1966 21,530 Urban Interstate I-89 NB over Connecticut River,Necrr
Grafton 1966 20,545 Urban Interstate I-89 SB over Connecticut River,Necrr
Hillsborough 1928 16,809 Urban other principal arterial Canal Street over Nashua River
Rockingham 1935 16,254 Urban other principal arterial US 1 over Par
Rockingham 1936 16,138 Urban other principal arterial US 1 over Par(Abd)
Belknap 1933 15,176 Urban minor arterial US 3 over Nhrr
Hillsborough 1958 14,701 Rural arterial US202,Nh101 over Contoocook River
Hillsborough 1921 14,690 Urban minor arterial US 3 over Souhegan River
Hillsborough 1933 14,392 Urban minor arterial US 3 over Baboosic Brook
Grafton 1977 14,340 Urban minor arterial US 4,Mechanic St over Mascoma River
Belknap 1962 13,715 Rural Interstate I-93 NB over Salmon Brook
Carroll 1955 11,920 Rural arterial US302,Nh113 over Conway Lake Outlet
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 208 119,490 1,972,175 1 99 13,715
Rural arterial 122 54,832 1,115,839 11 5,576 98,798
Rural minor arterial 165 61,088 795,083 9 2,418 46,172
Rural major collector 199 67,022 563,335 21 9,652 49,512
Rural minor collector 180 36,844 249,769 11 3,786 11,942
Rural local road 853 110,671 302,348 97 8,777 41,480
Urban Interstate 163 209,373 5,250,834 8 9,496 250,289
Urban freeway/expressway 92 118,772 2,910,665 5 4,616 102,658
Urban other principal arterial 113 162,158 1,885,333 5 11,137 85,553
Urban minor arterial 134 104,041 1,538,438 15 13,283 193,776
Urban collector 119 58,500 689,756 12 6,055 76,652
Urban local road 166 47,542 274,981 20 3,484 27,188
Total 2,514 1,150,333 17,548,556 215 78,378 997,735
Type of Work Number of Bridges Cost to Repair
(in millions)
Daily Crossings Area of Bridges
(sq. meters)
Bridge replacement 2,447 $5,996 17,533,889 1,144,342
Widening & rehabilitation 0 $0 0 0
Rehabilitation 10 $4 405 794
Deck rehabilitation/replacement 1 $1 50 180
Other structural work 4 $11 11,007 2,210
Total 2,462 $6,012 17,545,351 1,147,526

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.

17
Compared to 17 in 2019

in the nation in % of structurally deficient bridges

1. West Virginia 21.2%
16. Alaska 8.6%
17. New Hampshire 8.6%
18. Nebraska 8.5%

42
Compared to 43 in 2019

in the nation in # of structurally deficient bridges

1. Iowa 4,571
41. Wyoming 218
42. New Hampshire 215
43. New Mexico 207

20
Compared to 13 in 2019

in the nation in % of structurally deficient bridge deck area

1. Rhode Island 21.0%
19. New Jersey 7.0%
20. New Hampshire 7.0%
21. Washington 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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