Currently in the United States, there are 55,707 bridges that are structurally deficient. Inspections to bridges are infrequent and usually rely only on visual evaluation. But what if we could determine a bridge’s structural health using a sensor already in our pockets?

Our scientific results show the power of smartphones as an inspection device.


trips occurred each day in 2016 across a structurally deficient bridge

* Data from the U.S. Department of Transportation, Federal Highway Administration, Office of Bridge Technology. National Bridge Inventory 2016, Deficient Bridges by State and Highway System.

Bridges are constantly vibrating in response to traffic, wind, and other dynamic loads. Sometimes these vibrations can be felt while standing on the bridge. The bridge's vibrations are transmitted from the road surface, through the tires, into the suspension system, and vehicle cabin. The vibration sensors located in the vehicle can capture traces of the bridge's structural dynamics.


More than 170,000 people cross the Golden Gate Bridge everyday. Most of them own a smartphone that is able to record bridge vibrations using the onboard accelerometer creating a large network of mobile sensors! With only 2 mobile sensors we can obtain spatial information 120x more precise than 2 fixed sensors.


Visual inspection:
infrequent and very local


Fixed sensors:
rich temporal information but poor spatial coverage


Mobile sensors:
large spatial and temporal coverage


Do you have a smartphone? Do you want to help your state restore its bridges?

Collecting bridge vibration data is super simple!