>I think someone should try banning absolutely everything but emergency vehicles. No cars, no taxis, no vans, no trucks. Only cargo bikes, hand carts and maybe palanquins.

This is honestly crazy. No modern city in the world could function this way. How is cargo going to get moved around? You can't stock a supermarket with cargo bikes, and even in a dense, walkable city like Tokyo where I live, lots of cargo needs to be moved around, especially to stores, but also for cargo deliveries to other businesses and homes. And with no trucks or vans, how do you do stuff like building construction and repair?

Sure, you could get rid of private cars, and even taxis, and reduce 75-95% of the traffic on the roads, then make the roads narrower, add bike lanes, etc., but you can't just keep out cargo vehicles. No one's going to build a skyscraper or large apartment building using cargo bikes and hand carts.