Age of State Highway System Bridges


Source: SDDOT Office of Bridge Design, 2022 National Bridge Inventory data.

Photo left-hand side: Bridge construction began on the new Pierre-Fort Pierre Bridge in 2021
Photo right-hand side: Forest City Bridge over the Oahe Reservoir

There are 1,819 Bridges on the State Highway System

  • The majority of state-owned bridges are inspected once every two years, as required by the federal National Bridge Inspection Standards (NBIS).
  • Nine bridges are inspected yearly, including six over the Missouri River.
  • The Federal Highway Administration allows South Dakota to inspect certain low-risk state-owned structures, such as reinforced concrete box culverts and concrete rigid frame bridges, once every four years.
  • The SDDOT checks all elements required by the NBIS, plus additional elements not required by the NBIS.
  • The SDDOT also is responsible for ensuring that bridges owned by South Dakota’s local governments are inspected regularly and in accordance with the NBIS, usually by private engineering companies.

98% of state-owned bridges were in fair or better condition in 2022. This metric replaces the average sufficiency index as SDDOT's foremost measure of overall bridge conditions.


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