David Roberts:

As these vehicles inch tantalizingly closer to reality, we are starting to imagine an entirely new transportation system, in which self-driving electric vehicles are organized into shared city fleets, and dispatched by smartphone to satisfy transportation demand. In this brave, new world, there’s no need for private vehicle ownership.
 Yet, while we can envision a safer, more livable utopia, we can also imagine a dystopia, clogged with yet more cars and congestion. We know huge, fundamental transformation is coming to our transportation system, but it remains maddeningly difficult to predict exactly what shape those changes will take.
 Our transportation system has not changed much, except to become bigger and more sprawling, in over 60 years. There are so many moving pieces today, so many new technologies and possibilities, that it seems impossible to wrap your head around what may be coming.