More than 43,500 U.S. bridges are in poor enough condition to be deemed “structurally deficient,” according to the new report by the American Road & Transportation Builders Association (ARTBA).

Those bridges are crossed 167.5 million times a day.

Chunks of concrete fall from bridges with some regularity, and routine inspections often reveal problems that prompt authorities to shut down lanes of traffic or close off a bridge to heavy vehicles, to reduce the weight burden.

A bridge collapse last week in Pittsburgh — on the same day President Biden visited the city to talk about infrastructure — highlighted the problem, but engineers say it’s a bigger issue than many Americans may realize.