I've been observing their behavior in Atlanta for about the past year. Our roads here are fairly curvy, hilly, and lacking of expected markings, yet I haven't seen a driverless Waymo vehicle make a single odd move. One thing that brought a smile to my face was when I came to a 4-way stop at the same time as a Waymo vehicle at night & I flash my brights to tell the other vehicle to go ahead (southern hospitality) and I see the Waymo immediately begin its course through the intersection. I was so jolted that I began to tail it in order to pull up next to it to see if there was a human behind the wheel. Watching it drive down this slowly descending hilly road with intermittent speed humps and cars parked alongside the main right lane gave me a close up view of its slightly curving trajectory and braking behavior with regard to the humps. My thought on human or not was inconclusive until we reached a red light, and as I shot my eyes over and saw an empty driver seat, I smiled widely knowing that the software responds to brights flashed at 4-way stops (please don't tell me it doesn't and it just saw me indecisively not initiate at the stop). Thanks for reading