Uber users in Austin now have a choice between a Waymo robotaxi and a human driver. The two companies officially launched Tuesday the "Waymo on Uber"

The Alphabet unit starts commercial operations in its fourth city, where rides can be booked with Uber’s app. Uber is also providing charging and maintenance services.

Waymo brings its robotaxis to Tesla’s home town of Austin, Texas, via the Uber app. And one other big city will see Waymo cars later this year.