This is a silly concept as well. Effectively this sees us all cram as close to the city centre as possible to cut down journeys.That's the whole concept of the 5 minute city. Nobody is more than 5 minutes from any public service, cutting down the need to drive.
The sprawling conurbations and suburbs where everyone drives an hour or more just to fire off emails when they can do this from home is really unsustainable
Truth is, this concept is used in 3rd world countries and was widely used in the UK until just over a century ago until personal transport allowed people to escape the inner city slums.
When was the last time you actually drove into a city centre? The cities these days are so large that the centres are often 10mins or more from the outskirts. Imagine adding extra rings of communities attached to the already sprawling cities, they would become monsters of concrete and pollution, not from cars but just from humans living so close together.
Where and how would all these people live...High Rise flats? Not a new concept either and not a good one!
It's just more unrealistic thinking and all based on spending billions on infrastructure, pouring concrete on fields and forcing people close together. How long would all this take? Decades, unless we throw up prefabs like the 1950's, they were a good idea...
Also let's not forget, as others have pointed out here, all this investment and upheaval to take cars off the road when cars are not the main or worst culprit, just the most visual and most used by politicians and activists.
If billions were to be spent on anything, it should be on nuclear international goods transportation, not like we haven't had the tech for 50 years or more is it.