It has much less to do with inequality, and much more with zoning patterns in North America (and few other countries). I am not so sure about that, but it may a

It has much less to do with inequality, and much more with zoning patterns in North America (and few other countries). I am not so sure about that, but it may actually be reverse - the richer people may choose to live far away, and drive, in most cities. If inequality had anything to do with it, you would expect more unequal (or more expensive) cities to be more sprawling - as people are "pushed out" further by higher prices; but that is not the case. Why? Probably because people actually want to live far away, or don't care either way if they can trade off for e.g. more space, so they do (disclaimer: not me until 2020). Similarly, you would expect more unequal cities around the world to be sprawling, with more driving. Yet, many cities where the central area is unaffordable to locals do quite well with transit. Related to the above, many do have a ton of people who drive, and they may make up in low speed/inefficiency what harm they fail to produce because they don't drive as far. Again, because people, apparently, want to drive as soon as they can afford it (disclaimer: not me).