Why it matters: Aging infrastructure like bridges has been a serious issue in many countries, with collapses causing dozens of injuries and deaths in recent years. Researchers have started monitoring bridge integrity with driver's smartphones, which is cheaper than conventional methods but introduces privacy concerns.

Researchers from MIT and the US Military Academy recently published a study on the use of crowdsourced data from smartphone accelerometers to track the structural integrity of bridges. The method could significantly increase the lifespan of a bridge by letting owners know when something is wrong before a bridge is damaged or collapses.

Massive man-made structures like bridges and skyscrapers each have a unique modular frequency – like a signature for how its vibrations affect things on and around it. Some builders install sensors on bridges to monitor changes in modular frequency and detect changes. However, a large bridge might need many expensive sensors that themselves require maintenance, and responsible parties might need to manually and periodically download the sensor data.

The smartphone accelerometers in the many vehicles that pass over a bridge each day can detect those modular frequencies and send a significant amount of data to a bridge's owner. The method would be cheaper and easier than installing sensors and downloading their data. The variety of vehicles and mobile devices might impact the precision of their data, but a structure's consistent modal frequency could help stabilize the results.

However, ordinary users might not want their device's location and accelerometer data going to researchers or infrastructure authorities. Theoretically, they could introduce an opt-in system or even compensate the public for helping maintain the bridges they use.

More realistically, mobile accelerometer data might come exclusively from publicly-owned vehicles like police cars or mail trucks. Transportation and logistics companies could also agree to provide this data from trucks and delivery vehicles. Researchers gathered information from Uber drivers on the Golden Gate Bridge.

Although drivers' accelerometers can detect modular frequency changes in bridges, determining what's causing those changes is another matter. Researchers say they can isolate for changes in temperature, which will likely reduce false positives.

According to the study, incorporating crowdsourced data in a new bridge's maintenance plan could add over 14 years to its lifespan at zero additional cost.