In the dark age before electricity, great mills were located adjacent to waterfalls to provide direct energy. This is the origin story of many early industrial revolution cities including Minneapolis. The development of the electric grid, first DC, then AC, untethered milling from the falls.
In the age before the streetcar, people lived within walking distance of their jobs. Downtown was very important. With the streetcar and subway, downtown remained important, as the destination of a radial commuting, shopping, or entertainment trip beginning farther out in suburbs. But with the automobile, not only residences, but first shops and then workplaces could become untethered from their downtown anchor at the head-end of the transit system. Downtowns in many US cities haven’t added employment in many decades, and almost all have lost market share.
Yet the individual’s daily activity pattern itself was still confined to a roughly 30 minute radius (sometimes referred to Marchetti’s constant, but identified by Zahavi and others earlier). This helped glue cities together.
With soon-to-be-deployed mobility technologies like Automated Vehicles (AVs) this commuting budget range can expand. Thirty minutes of actively engaged traveling (driving, biking, walking) is not the same as thirty minutes as a disengaged passenger in a (commuter train or) autonomous vehicles.
With new and better telecommunications technologies — which admittedly people have been talking about this for ages, but which are steadily getting better — the requirement for in person meetings steadily drops. With fewer in-person meetings, there are fewer days per week that one needs to “go” to work, which means a weekly commuting budget may be a more appropriate concept than a daily one. It also means off-peak travel is more likely. Non-work trips are likely to substitute in part for work trips, but they won’t be as long or as peaked. With less congestion in any case due to AVs and changes in demand patterns, roads are faster. All of which suggests even more decentralization of residences and less physical tethering between home and work.
Telecommunications also no longer requires wires, as wireless gets more efficient. So the need to be on the wired telecom network is not required.
Rooftop solar energy is increasingly becoming feasible. Without the need to attach to an electric grid (though maybe still wanting to due to load balancing – though with enough energy conversion efficiency this doesn’t matter), and with more power available on large rooftops where land is less scarce, score one more for decentralization.
Even in the absence of flying cars, though most certainly with it, the costs of living in isolation and physically unconnected from the city drop. The consequence is a greater trend toward decentralization. Sorry urbanists.
Now the urbanists will say, rightly, that cities are getting better too. While life for the disconnected may be improving, the quality of life for highly tethered urbanites might also be rising. Urban pollution will drop as renewable energy and electric vehicles become standard and social amenities will always be closer in terms of travel time.
Where anyone will live depends on their preferences and the opportunities available to them. The good news is advances in technology suggests more opportunities will be available. The bad news is your opportunities depend on the preferences of others. I can’t be alone in wanting to live a city of 100 million people (imagine the specialization in food, stores, and entertainment possible at that scale) and expect to be able to satisfy that want. I need more than 99 million of my closest friends to agree.