I love this approach. It would be great to have 100s of these on more or less predefined trajectories, but without a set schedule. Just press a button and one shows up a few minutes later, perhaps with already some passengers going similar routes. It could help anchor urban development, something a pure self driving car would not too, and the absence of a set schedule removes the biggest drawback of public transportation. They can also just use existing roads, no need to construct a separate track. I hope these things would help introduce affordable public transportation in many US cities, and actually be useful and practical.