Your Phone Can Determine If a Bridge Is Busted

Because you’re a very responsible person who doesn’t text and drive, when you roll over a bridge your smartphone is stuck to the dash, where it is perhaps giving you directions while streaming a WIRED podcast. But in the background, your device is also gathering reams of accelerometer data. One day, this could help diagnose problems with the very bridge you’re speeding across.

Every bridge has its own “modal frequency,” or the way that vibrations propagate through it—then subsequently into your car and phone. (Tall buildings, which sway in the wind or during an earthquake, have modal frequencies too.) “Stiffness, mass, length—all these pieces of information are going to influence the modal frequency,” says Thomas Matarazzo, a structural and civil engineer at MIT and the United States Military Academy. “If we see a significant change in the physical properties of the bridge, then the modal frequencies will change.” Think of it like taking a bridge’s temperature—a change could be a symptom of some underlying disease. 

In the US, much of the bridge…