The Most Common Bridge Types in America

The United States has 624,191 bridges in the National Bridge Inventory, but they are not all built the same way. The NBI records the structure type of each bridge, revealing which engineering designs dominate the American landscape. Understanding bridge types helps explain why some bridges age differently than others and why maintenance strategies vary.

1. 1 -- 181,919 bridges (29.1% of total). Average age: 53 years. Poor condition rate: 4.7%.

2. 5 -- 144,486 bridges (23.1% of total). Average age: 36 years. Poor condition rate: 3.6%.

3. 3 -- 119,159 bridges (19.1% of total). Average age: 55 years. Poor condition rate: 14.6%.

4. 2 -- 78,372 bridges (12.6% of total). Average age: 52 years. Poor condition rate: 3.8%.

5. 4 -- 51,159 bridges (8.2% of total). Average age: 50 years. Poor condition rate: 6.4%.

6. 6 -- 30,033 bridges (4.8% of total). Average age: 32 years. Poor condition rate: 1.2%.

7. 7 -- 14,853 bridges (2.4% of total). Average age: 58 years. Poor condition rate: 23.3%.

8. 9 -- 2,428 bridges (0.4% of total). Average age: 30 years. Poor condition rate: 5.8%.

9. 8 -- 1,386 bridges (0.2% of total). Average age: 120 years. Poor condition rate: 19.9%.

10. 0 -- 396 bridges (0.1% of total). Average age: 40 years. Poor condition rate: 6.1%.

Different bridge types age differently. Concrete bridges tend to be durable but can develop cracking and spalling over time, especially in freeze-thaw climates. Steel bridges are strong but susceptible to corrosion if not properly maintained with paint or protective coatings. Timber bridges are less common today but still found in rural areas and parks; they require regular treatment to prevent rot.

The poor-condition rate varies significantly by type. Older steel truss bridges, many built during the early Interstate era, tend to have higher poor-condition rates because of their age and the difficulty of maintaining complex steel connections. Modern prestressed concrete bridges generally have lower poor-condition rates because of the material's inherent durability.

Explore detailed information about each bridge type -- including how they work, their advantages, and real examples -- in our [bridge type encyclopedia](/types). Or dive into the data by state with our [state report cards](/reports).