The idea, as far as I understand, is that the tunnels present new underground routes that can use central control of vehicles to manage congestion.
According to Elon, his investment in cheaper drilling tech will mean we will have many tunnels with relatively cheap to build entrance and exit points that are significantly smaller than subway stations.
These entry points will allow you to drive to and from your house, enter the tunnel system where some sort of conveyor belt/computer controls your car. You exit the tunnel and drive normal.
So the idea is that the tunnel exits will be _very_ near to your home. Otherwise it's dumb. I think what you are saying about large predictable roads is basically what Elon Musk is proposing but underground.