Natural gas pipeline leaks that pose a safety hazard are quickly addressed. But what about leaks too small to pose a threat? These mall leaks are often overlooked and they collectively release tons of methane, a greenhouse gas 84 times more potent than carbon dioxide.

However, thanks to researchers from Colorado State University, the University of Northern Colorado, and Conservation Science Partners—who’ve teamed up with the Environmental Defense Fund—a small unit of Google Street View cars are turning into mobile methane sensors to monitor leaks that have flown under the radar.

Lead researcher Joe von Fischer, a biologist by training, originally bought a laser spectrograph, which scans invisible gases that are opaque under infrared light, a decade ago to use on the Arctic tundra. That is, until he one day decided to put it in his car and drive around Fort Collins. He ended up finding a local methane leak with his mobile amalgam of a methane sensor.

“At the same time, Google was interested in putting some of these new methane analyzer analogs in their vehicles, and the Environmental Defense Fund was interested in methane because it’s so poorly quantified,” says von Fischer.  Naturally he was put in charge of the project.

Since then, their collaboration has seen sensor-equipped Street View cars map methane leaks in pipelines beneath the roads of 14 cities throughout America, releasing the data publicly as citywide maps online. The initiative has even helped spur one New Jersey utility provider to commission a $905 million upgrade to gas lines.