US 4 over Smith River

Merrimack County, New Hampshire · rated Poor in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

• US 4 over Smith River in Merrimack County, New Hampshire, is rated in poor condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the superstructure, rated 4 (poor condition) on the 0-9 scale.
• It was built in 1929 and reconstructed in 1991, making it 96 years old at the 2025 inventory.
• It carries about 2,087 vehicles a day (traffic count year 2023).
• Its listed owner is the state highway agency.
• It is one of 27 of the 326 inventoried bridges in Merrimack County rated poor (8.3%); 27 (8.3%) are rated poor.
• A poor rating means at least one major component - deck, superstructure, or substructure - is rated 4 or lower on FHWA's 0-9 scale. It does not by itself mean the bridge is unsafe; bridges judged unsafe are closed or load-restricted by their owners.

View this bridge on a map → (43.5299, -71.86989)

Component ratings

Bridge details

Source: FHWA National Bridge Inventory, 2025 data as reported by the New Hampshire department of transportation.

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Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.