That said, it might be a good long while before Amazon drivers sport smart glasses — if they ever do. Adding displays to ordinary glasses or audio-based smart glasses like the current Echo Frames is also a tough engineering challenge — one that many companies have failed at. Amazon is reportedly having issues making glasses with a battery that can last a full eight-hour shift while also being light enough to wear all day. Another problem is many people already have corrective lenses, and thus far, consumer smart glasses haven’t always been capable of accommodating every prescription. It’ll also have to convince its entire fleet of drivers — many of which are third-party contractors — to adopt the technology. It could take years for Amazon to gather enough data on that last 100 yards (i.e., building layouts, sidewalks, streets, driveways, etc.) to make its vision a reality.