Earlier quoted context omitted.
Self-driving cars are modern public transit. "Train brain" is old thinking that public transit should take billions of dollars and decades to make fixed-route trains that only get travelers part of the way to where they actually want to go.
And building 20 lane highways doesn't take billions of dollars? Putting even more cars on the roads doesn't sound like it would scale well. Aren't they already massively overloaded?
Building highways is very expensive, but much much less expensive than new rail. The most cost effective and environmentally sound thing to do is to make the most possible use out of existing infrastructure. As safe and predictable drivers (no fast stops and starts, swerving, or accidents), Waymo smooths traffic for everyone.