Isn't that Musk's (with Boring + Tesla) whole game plan? The demo https://www.youtube.com/watch?v=u5V_VzRrSBI, I think is pretty explicit about that. The difference is that you own the 'cab' and you don't have to time any 'transit sync moment'.

If I'm not mistaken you are basically thinking of a circuit-based network (with ad-hoc 'datagrams') while Musk seems to be going for a completely datagram based network. It's an utterly genius idea, at least from a theoretical standpoint (I have no knowledge of the economic aspect).