Elevators and trains are not even in the same ballpark as cars, and the busses you linked to can't function on public roads. They don't have the ability to interact with other vehicles.

It's entirely valid to state that we can do lots with our current tech, because we can, but when the topic is self driving cars on public roads, it makes no sense to claim they're possible without general AI based on the fact that an existing bus can drive around a closed course.

Giving those busses the ability to navigate arbitrary situations on public roads is not simply an incremental improvement, it requires that you solve a fundamentally different problem.