The Google Streetview cars you see driving around your neighborhood are taking more than just pictures. Google has affixed sensors to their cars that detect natural gas leaks that are more common in the US than you might think—the cars picked up a leak every few blocks while driving through Central Boston. While the leaks it detected weren’t large enough to cause an explosion, they were still emitting small levels of harmful methane. The program was part of a program run by the Environmental Defense Fund that aimed at minimizing unknown greenhouse gas emissions.