So imagine this. Privately owned gas-powered cars are banned downtown, replaced by fleets of electric, app-summoned self-driving taxis. These autonomous-and-shared pods are in constant circulation, allowing most of the city’s parking lots to be reclaimed for real estate or parks. Air quality improves, greenhouse gases decrease. That seems to be a vision of the future a number of car manufacturers and tech companies are angling toward, judging from a flurry of recent auto-tech news.