NH175 over Mad River
Grafton County, New Hampshire · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- NH175 over Mad River in Grafton County, New Hampshire, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1927, making it 98 years old at the 2025 inventory.
- It carries about 2,020 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 242 of the 547 inventoried bridges in Grafton County rated fair (44.2%); 43 (7.9%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- Its condition class and component ratings are unchanged from the 2024 inventory.
- Its most recent inspection on record is dated May 2024, on a 24-month routine inspection cycle.
- A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.
View this bridge on a map → (43.86173, -71.63228)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 6 | 6 | Satisfactory condition |
| Superstructure | 6 | 6 | Satisfactory condition |
| Substructure | 5 | 5 | Fair condition |
Bridge details
| Structure | Concrete deck arch |
| Length | about 85 ft |
| Location | 6.6 Mi N Jct US 3 |
| NBI structure number | 003501530014700 |
| Condition class | Fair |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | May 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 8: foundations stable, scour above the top of the footing |
Source: FHWA National Bridge Inventory, 2025 data as reported by the New Hampshire department of transportation.
Busiest bridges in Grafton County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-89 NB over Plaza Connector Road | 2012 | 28,690 | Fair |
| I-89 Nh 10 over Brook Atv Trail | 1959 | 25,062 | Fair |
| I-89 Nh 10 NB over Truck Road Mascoma River | 1966 | 23,084 | Fair |
| I-89 NB over US 4 Nh 10 | 1966 | 22,727 | Good |
| I-89 NB over Connecticut River Necrr | 1966 | 22,288 | Poor |
| I-89 Nh 10 SB over US 4 | 1966 | 21,937 | Good |
All bridges nearby: Grafton County, NH bridge conditions · every bridge in Grafton County · New Hampshire bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.