I don’t know about the equipment of Waymo cars, but I would be surprised if they didn’t have LIDARs or some other form of distance based environment detection.
And that should be sufficient to implement basic obstacle detection. You don’t need to use machine learning if you can use sensors telling you that “something is too close”.
Your first error was to create a reddit app.
Your second error was to not create or contribute to a Lemmy app instead.
Hope that helped. :)