What world do you live in? In my world, cars are extremely inconvenient. They're expensive, the parking is very limited and expensive, and to go anywhere you usually have to take toll roads, which are expensive. As a result, most people don't have a car, and use the subway, or take trains between cities.
>apan also has tunnel infrastructure for cars. one of my most vivid memories of visiting there is driving in and out of many-miles-long tunnels, and coming out of the last one smack dab in the middle of kobe. it was magical.
They're not highly common in Japanese cities. There are a bunch of car tunnels in the mountains though (no subways there). They tend to be really narrow; there's no way to pass in them.
>then we can also strategically reduce street area dedicated solely to cars (particularly street parking
Do you have any clue how much it would cost to build gigantic underground parking garages? Or how much the parking fees would be? This is lunacy.