In the long run, it would be best to reduce need of travelling, it is not only moving to another location that consumes resources and energy, but everything else, eating and consuming as it is really difficult to even eat well, yet 'green' when at unknown places.
Everyone should have piece of land where everyone would get at least part of food, amount of people would then need to adjust to available ground area, it would take out many issues, even need for mass transit and silly economy that is based to constant growth.
Of course it would not be very realistic or fun, but it would greatly bring human closer to nature so human could understand nature better and live with nature instead living from nature.
Anyway, as every country seem to be so afraid of terrorism that they stomp on any amount of persons just to keep mass transit safe, it will probably cause huge problems and greatly decrease any interest to be near anything mass something, mass transit, mass events etc.
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