Mounted sensors can detect vibrations in bridges that indicate their health, but so can ordinary smartphones. The key is in the phones’ accelerometers, which detect and gauge movement as the phones pass over the bridge under a system developed by researchers at the US Military Academy at West Point, N.Y.



Engineers could measure the health of bridges using data from smartphones, which could allow us to add up to 15 years to the usable lifetimes of these structures.

Most bridges are assessed using visual inspections, which can be a time-intensive process. Alternatively, mounted sensors can detect vibrations, called modal frequencies, which are tied to the bridge’s physical characteristics and can be used to assess its health, but it would be expensive to put these on all bridges.

Now, Thomas Matarazzo at the United States Military Academy at West Point, New York, and his colleagues have developed a system to measure modal frequencies, and so monitor bridge health, by using movement data from phones. “We don’t have to purchase any additional or special sensors to be able to collect the data that we need to at scale,” says Matarazzo.

To do this, the researchers collected data in an app from phones as they were taken over bridges. They used GPS location data and information from the phones’ accelerometers, which can reveal any tiny movements the phone makes.

The study was divided into three parts: in the first, the researchers mounted two iPhones in their cars and drove over the Golden Gate Bridge in San Francisco a total of about 100 times.

In the second, they took data from Uber drivers completing more than 70 trips over the Golden Gate Bridge as part of their day-to-day work. The researchers also used data from about 250 trips with Android smartphones over a short concrete bridge in Ciampino, Italy, which is more representative of bridges in the US.