> Hypothetically, if all the cars are synced, you eliminate certain congestion effects.
Sure if you also remove, people, bikes and everything else. Congratulation, you just invented a grade separation. And if you are going threw all the effort of grade separation, you know what a good idea? To push as many people as possible along that route. And you know how you do that, by not putting each human into a huge 2t box of steel.
If you had the incredibly inefficiency of cars, to grade separate you would need to grade separate a HUGE space. And grade separation is incredibly disruptive. Grade separation is only worth if you can push lots of people threw.
> Likewise, synchronized cars can drive closer to each other
Because synchronized cars never have a mechanical failures or emergency break?
Here is an idea, you create these things called 'couplers' and then you physically couple multiple 'cars' together and then you actually can be really close together.
How about this, we move away from cars, and have beautiful parks for the people who live in these places. with nice restaurants having seats in what is now the road, with some nice not so fast trams going threw. And then some nice high density rail under or over on a guide-way.
Here is a good video going threw all these points and how great this scenario actually would be.
https://www.youtube.com/watch?v=040ejWnFkj0