It is unfortunate that we use words like "urban" and "city" to describe fundamentally different built environments - i.e. everything from sprawling habitats constructed for the convenience of homo automobilicus to compact habitats scaled for the species homo pedestricanus.
Of course here in the United States the main thrust of our economic activity over the past 60 years has been to expand habitat for homo automobilicus - which inevitably undermines, destroys, and prevents the formation of habitat for homo pedestricanus. No surprise, the larger, faster, more powerful species homo automobilicus is now dominant in most communities. The dearth of human life on the sidewalks of villages and small cities throughout the US attests to the lost struggle.
This victory may prove short-lived, however. Having suffocated millions of acres of bioproductive land beneath the highways and parking lots it needs to move and store its colossal population, homo automobilicus is now appropriating even more land for “food” production (i.e. biofuels). But it is unlikely that homo pedestricanus will have to suffer this seizure for much longer. Why? Because homo automobilicus will eventually collapse from its rapacious appetite. With an average weight of several tons, and given the fact that it travels at much higher speeds over much longer distances than the small, slow, localized species homo pedestricanus, homo automibilicus has far larger energetic requirements. It is by nature a carrion feeder, and basic thermodynamic laws make it highly unlikely that Earth's sustainable energy flows will prove adequate fare for a population of hundreds of millions.
History will almost certainly show that petroleum was the largest, most nutritious dead carcass humankind will ever find on Earth. Cheap oil alone has allowed homo automobilicus to gorge and breed to wildly unsustainable numbers, and the end of cheap oil spells its demise.
One would hope this implosion will not prevent homo pedestricanus from flourishing once again. But why must it come to this? If only the species homo sapiens were to discover enlightened self-restraint!