> These included examples from Germany (where different regions had different urban/rural balance) and France (where rural had more CO2 emissions).

Not to being rude but such computations are not science, are just game based on arbitrary assumptions... A "TCO of pollution" need a damn large model who simulate all people consumption traced to their sources, counting relevant processes in between + simulate different theoretically realistic arrangements changing some parameters. AFAIK no such models exists probably simply because it's not much in fashion reasoning in global terms instead of focusing on single specific aspects and perhaps it's so long and complex that most fear anyone can spot small errors practically not really important, but weaponized to discredit the whole design...

> Do you have evidence for that? You need, what, 100 meter of street per house?

A simple empirical evidence: do a large Riviera need many simple roads or big dorsals? I mean why we need a big highway? Typically to connect a dense area to another because many people and goods travel from some "hub" (in network theory speaking) while a almost-hub-less network do need more small links to traverse it from anywhere to anywhere. Now if you agree with that try to imaging how impacting is building such expensive highways vs small roads. Not much in absolute terms (like how many rocks, asphalt etc you need) but in relative terms of local impact on climate and nature.

It's the same for a fully watertight city area vs a sparse urbanized one: both roads are watertight, but in a city there is a very large watertight surface who push water in few directions, in the riviera water goes everywhere so you do not get much "river" effect that alter local water system. Similarly for small roads you do not need to destroy entire mountains, create giant infra that alter local wind and so on.

> Flight is energy intensive. Either you have heavy batteries (making the flight even more expensive) or you've got hydrocarbons, which currently means fossil fuel.

Sure, so far, BUT that's anyway our path for various reasons, climate and social change included who need to move people and so having "movable infra", something not doable with roads or rails but doable by air and water. Also we have to compute the cost of vehicle + it's use vs crafting a whole road/rail etc infra and keeping it up. Again it's a damn complex model but it's not a new idea that by air is almost at the same cost even if we can't move anything by air... It's not me but
https://www.easa.europa.eu/sites/default/files/dfu/uam-full-... who claim that's the future. They claim for urban mobility but I think that's definitively crazy, while it's perfectly doable in a large riviera, and I doubt McKinsey do not have though that...

> Batched ground transport is more fuel efficient.

That's theoretically true, practically false: public transports are efficient when are a bit loaded, but to be effective they need to operate 24/7/365 witch means OR they accept to be far less efficient than private transports MOST of the time or they simply run only for efficient usages and so people need anyway a private transport and having both is still less efficient that using only one. Even in Swiss, to cite a fresh article: https://www.thelocal.ch/20230109/opinion-trains-in-switzerla...

> My point is that this means you don't have any cost sharing with your neighbors. Each house needs enough to cover its peak use, and likely each person need to know how to maintain the local equipment, and have the tools for the additional maintenance.

That's another classic problem, still unsolved. In the recent past for instance teleheating was sold as and eco-friendly cheap and simple way: you get hot water from some industry cooling systems who need to push heat out and you are happy. Now those who choose that path cry that their heating prices have skyrocketed... Similarly nowadays in UE homes are FAR cheaper than apartments in operational expense terms. The issue essentially is "if we are all smart and fair anything is simpler sharing stuff", but the big if tend to be valid for limited period of time...

The city water tower is a good example: in theory individual homes get water and have nothing but keep up normal home pipes. Nice. In practice it means that an accident on the system is a general emergency since anyone are without water. If you have a bit of reserve at home, EVERY HOME, than the emergency is far less urgent and so maintenance and design costs goes down. You do not need a hyper-quick team 24/7 ready to run, with anything needed immediately available for instance. For electricity it's the same: a spread Rivieras grid with homes capable of few hours autonomous power it's far less costly than a dense grid that must reduce downtime to the extreme. There is a storm and some transformers burn? Oh, no issue we will change them tomorrow vs push people in the middle of a stormy night with all they need to change it ASAP. We users do not feel those costs but they are still there.

> Actually, probably less because I would have more to maintain the house.

And how much time you save having cut the trip to the office ALL working days?

> You do know that many people like to be in the city for easy access to restaurants, clothes shopping, the library, clubs, socializing with friends, lectures, political demonstrations, parades, churches, festivals, and more, right?

Yes, BUT I know that if enough people flee the city those who want it can only keep it up alone, witch is a doomed to fail effort... BTW in terms of ease of access: try to move in a dense EU city and in a vast riviera... It's often easier do 100km in a riviera than 10 in a city. Personal experience...

> It's not like wide-scale ownership of personal automobiles is sustainable either. I mean, your lifestyle requires two cars. What happens if, due to age or illness, you no longer have the physical ability to drive? What do you do then?

That's a issue common everywhere: if we do not die young at a certain point we need help. But help in a riviera it's not much different than in a city, for instance it means having someone who gives you food, help you move etc, evolution is the answer: we are near self-driving cars, in the future even if not tomorrow, we will have them. In the future we will have likely much more automation that allow elders to remain autonomous for a larger timeframe of their life. Then... Than it's the same than today. At a certain point we can't live alone anymore. And that's why we have structure to help the elders, having them in a city or spread does just means having littler structures in nature instead of isolated concrete buildings where we can't almost see anything nice around...

However you are right stating that NOT EVERYBODY can afford certain homes, cars etc, and that's a problem I do not see solved by anyone. Those who claim goshiwong alike homes solve that tend to be some who want young and productive slaves, not anything else...