After last Thursday’s bridge collapse in Mount Vernon, Washington there has been a lot of talk about the condition of the now-fallen bridge. How safe was it? How could a strike to a single girder cause an entire section to fall?

While the National Transportation Safety Board (NTSB) is investigating the answers to these questions, you may be surprised to learn that the Skagit River bridge is not as bad as it gets.

There are 66,749 structurally deficient and 84,748 functionally obsolete bridges in the United States (including Puerto Rico), according to the Federal Highway Administration. 

That’s about a quarter of the nearly 607,000 bridges in the U.S. The crazier part? That number used to be around 30 percent in 2002.

A “structurally deficient” classification means that a large portion of the bridge is in poor condition or worse; whereas “functionally obsolete” means that the bridge wasn’t built to today’s standards.

Many bridges under these two classifications have spans that are “fracture critical,” meaning that one hit in the wrong place could have the entire bridge falling down. Fracture critical bridges lack redundancies seen in other bridges that could save the structure in the event of an unfortunately-perfect hit.

“Today, they’re still building fracture critical bridges with the belief that they’re not going break,” said Mark Rosenker, former chairman of the NTSB, to the Globe and Mail.

From the mid-1950s until the late 1970s, about 18,000 fracture critical bridges were built to complete the Eisenhower interstate highway system.

Why were they built this way? To save money and get the job done faster.

Now, the United States is facing a potential bridge integrity crisis. The Skagit River bridge had a 57.4 rating out of 100 — seemingly low to the public, but not in comparison to other bridges across the country — used to evaluate whether the bridge can remain open.

As the Globe reports, “hundreds of bridges in Washington state have worse ratings than the one that collapsed, and many around the country have single-digit ratings.”

A bridge needs to have a score of 50 or lower to get federal replacement funds, and a score of 80 or lower to receive federal rehabilitation funding.

Last year, the U.S. spent an all-time high of $28.5 billion on bridge construction, according to the American Road and Transportation Builders Association. However, the Federal Highway Administration’s National Bridge Inventory shows that over $316 billion is required to fix the nearly 202,000 bridges that need work (whether rehabilitation, widening or replacement).

So where is this money going to come from? The Federal Highway Trust Fund, which provides construction aid and funds to states, is expected to go broke next year.

The trust gets its funds from federal gas and diesel fuel taxes, but these numbers aren’t increasing as people are driving less, there are more fuel-efficient cars and —the big one — the federal gas taxes haven’t been raised since 1993.

By looking at these numbers, there’s a clear possibility that other bridges across the States could face a similarly unfortunate fate as the Skagit River bridge. As the police have said, it’s “miraculous” that no one died.