The comparison for costs is, for some reason, usually made by considering public transit mode (train) and infrastructure (tracks) but only the mode (car) for the autonomous solution. I’m not suggesting that auto infrastructure (roads) is cheaper than transit infrastructure, but I think it’s worth calling out that it’s important to compare apples to apples by including cost of roads upkeep, which is not insignificant.
On the argument of autonomous vehicles easing congestion, I definitely agree. I’m wondering, though, if there are any studies showing that autonomous vehicles will solve congestion. With an increasing world population and increasing densification of urban areas, less traffic could still end up being too much traffic. Are autonomous vehicles and, more specifically, autonomous vehicle networks able to keep up with increasing bandwidth demand? Would they beat public transit in the long-run?
Finally, on electric drive technology: No doubt that this can and will reduce overall emissions and help improve the environment. If we applied the same emission-reducing strategies to trains (e.g. electric or even solar-powered buses and trains), could we get the same or better efficiency than autos. I think it would be worth exploring whether this is a better use of government dollars.