So, imagine you are driving along in your fancy high-tech car, minding your own business, with your yet-to-be-feature-complete full self-driving software activated, and suddenly the car slams the brakes to a full stop, like a donkey that had an epiphany that what it was doing just didn't serve any purpose and therefor just refused to move any further. Sure, it's great that something useful is becoming of outdated fossil fuel vehicles. Giants having fun with them riding down hills seem like a good solution, and I guess they don't burn gas in the process, but my car might get nervous around these guys. For the time being, my car didn't stop, but when the brain of the car gets more clever than that of a cricket, it might recognize the car, and panic! It does so already when it sees broken off tree branches laying on the side of the road.