Then why underground? Just put car on electric platform and ferry across existing highways. Just need a very large area for loading and offloading cars otherwise you get the same traffic jam waiting your turn for other cars to get on or off the platform.
But if you’re super rich and a city lets you build your own tunnel why the hell not lol.
There is an OTR Sci-fi drama I heard recently called “The Roads Must Roll” if I remember right.
Everyone moved by giant conveyors.
Then why underground? Just put car on electric platform and ferry across existing highways.
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How would that add capacity? Plus there’s a speed limit and traffic jams on existing highways.