How many structurally deficient bridges are in the US?

According to the FHWA National Bridge Inventory, over 42,000 bridges in America are classified as structurally deficient. That represents roughly 7% of the nation's 624,000+ bridges.

Does structurally deficient mean a bridge is unsafe?

Not necessarily. Structurally deficient means one or more key components are in poor condition and need repair. These bridges are still inspected and may have weight restrictions, but they are not immediately dangerous. However, they do require attention to prevent further deterioration.

Which states have the most structurally deficient bridges?

States with the highest percentages of structurally deficient bridges include Iowa, West Virginia, Pennsylvania, South Dakota, and Rhode Island. Rural states with large bridge inventories and limited funding tend to have the highest deficiency rates.

How much would it cost to fix all structurally deficient bridges?

The American Society of Civil Engineers estimates the backlog of bridge repair needs at approximately $125 billion. The 2021 Infrastructure Investment and Jobs Act allocated $40 billion specifically for bridges, but this covers only a fraction of the total need.

America's Structurally Deficient Bridges: Where They Are and Why It Matters

What Structurally Deficient Actually Means

The term "structurally deficient" is an official FHWA classification applied to any bridge where the deck, superstructure, or substructure receives a condition rating of 4 or below on the NBI's 0-9 scale. A rating of 4 indicates "poor condition" with advanced deterioration that affects structural integrity. On our A-F grading scale, these bridges typically receive D or F grades.

It is critical to understand that structurally deficient does not mean imminently dangerous. These bridges are still legal to cross and undergo regular inspections. Many have weight restrictions posted to limit stress on weakened components. However, they represent a backlog of deferred maintenance that grows more expensive to address with each passing year.

Where Deficient Bridges Are Concentrated

Structurally deficient bridges are not distributed evenly across the country. Several patterns emerge from the NBI data:

The Rust Belt and Appalachia — Pennsylvania, West Virginia, and Ohio have some of the highest raw counts of deficient bridges, reflecting aging industrial-era infrastructure and harsh winters.
Rural Plains states — Iowa, South Dakota, Nebraska, and Oklahoma have high percentages of deficient bridges. These states have vast rural road networks with thousands of small bridges over creeks and drainage channels.
New England — Rhode Island and Connecticut have relatively few total bridges, but a high percentage are in poor condition due to age and exposure to corrosive marine air and deicing chemicals.

By contrast, states like Nevada, Texas, Arizona, and Florida tend to have lower deficiency rates. Many of their bridges were built more recently, and warmer climates reduce freeze-thaw damage. You can explore state-by-state data on our state pages.

Why Bridges Become Deficient

Bridge deterioration is driven by a combination of factors that compound over time:

Age — The average age of America's bridges is 44 years. Many were built during the Interstate Highway era of the 1950s-1970s with design lives of 50 years. We are now beyond that lifespan for tens of thousands of structures. See our list of the oldest bridges still in service.
Increased traffic — Bridges designed for 1960s traffic volumes now carry far more vehicles, including heavier trucks than originally anticipated.
Environmental exposure — Freeze-thaw cycles, road salt, humidity, and coastal air all accelerate corrosion and material degradation.
Deferred maintenance — When funding is tight, routine maintenance gets postponed. Minor cracks become major structural problems. The ASCE Infrastructure Report Card has consistently flagged this pattern.

The Economic Impact

Structurally deficient bridges impose real economic costs beyond repair expenses. When a bridge is weight-restricted or closed, trucks must take detours that add miles, fuel costs, and delivery time. The American Road and Transportation Builders Association estimates that structurally deficient bridges cost American drivers $9 billion annually in additional vehicle operating costs and lost time. For rural communities, a single closed bridge can mean a 30-mile detour to reach a school, hospital, or market.

What Is Being Done

The 2021 Infrastructure Investment and Jobs Act included $40 billion specifically for bridge repair and replacement — the largest dedicated bridge investment in American history. The new Bridge Formula Program directs funds to every state based on a formula that accounts for the cost of replacing structurally deficient bridges. Additionally, the Bridge Investment Program provides competitive grants for economically significant bridges.

However, the total backlog of bridge repair needs is estimated at $125 billion, meaning the new federal investment covers roughly one-third of the shortfall. State and local governments must continue to fund the remainder. You can see how individual states compare on our state condition rankings.

How to Check Bridges Near You

Every bridge in the NBI database has a public record that includes its condition rating, inspection date, and structural details. Search our database by name, location, or route to see its current grade and full inspection history. Our glossary explains all the technical terms used in bridge condition reports.