Identifying maintenance needs for subway tracks is a labor-intensive process.Recently, Google teamed with NYC to see if Pixel phones could use their sensors to cheaply spot problem areas.Over a four-month test, the Pixel phones detected 92% of problems later confirmed by experts.Your smartphone is utterly packed to the brim with sensor of all kinds. Some of those are out in the open, like the cameras our phones use to image their surroundings, while others are hidden within, like the accelerometers that tell our phones what direction we’re holding them. Collectively, these sensors can be used by clever software to deliver all sorts of useful features, like how Pixel phones are able to detect when we’re in a car crash and summon emergency assistance. But now we’re hearing about how those same sensors are keeping some much larger vehicles safe, with New York City’s Metropolitan Transportation Authority (MTA) tapping Pixel phones for some help with subway maintenance.The MTA’s got a big job, responsible for keeping the population of the country’s biggest city moving around without clogging the streets with an impossible number of cars. But running a subway system this expansive means there’s a lot of track that you’ve got to keep safe and operational — some 665 miles of it.