It's insane to start a new rail project at this point in time, IMO. Total waste of money.
That is utter nonsense. The physics of how many cars you can fit on a road, how fast you can get from A to B and the distribution trip patterns won't change that much.
The basic capacity of a busy road is not significantly less than that of a train, and we already have thousands of roads. We just don't use them very intelligently.
Or, to put another way: a fleet of networked autonomous vehicles is a train. Put money into making that happen, and I'll vote for it. I'm definitely not voting for $50 billion choo-choo trains, or whatever 1890s-era solution the urban transit planners in Seattle are dreaming up this week.
What you get from autonomous vehicles is improved flexibility, and that improves all transit modes while only slightly changing the dynamics that make rail vs. bus vs. car interesting.