From an ecological perspective, highways and automobiles cause more damage than many other actions man performs. Expediting the transition to sky cars will not only allow ecosystems to exist as they once did (i.e. without an interstate highway cutting them in half), but will also allow us to spend less money on maintenance. Plus, sky cars would be faster, easier to implement autopilot functions on than street cars, and could totally revolutionize society in many other ways. If we actually invested in this idea, we could have the first cars flying around out there in 5-10 years, maybe even less. There are already a number of companies out there with promising prototypes.