Yowch! Yeah, I had a time when I needed to make a u-turn, and I waited until a semi passed through the intersection, then made my (legal) u-turn... only to find that the semi had braked, entirely, and was sitting in his lane. I was able to stop in time, but I definitely hadn't expected that. THEN he decided to start backing up! I think he'd passed a gas station and wanted to get into it. I have never been very good at managing to get the horn to honk when I want it to (it takes a lot of pressure, so when I want a light honk it does nothing at all), but that time I put all my weight on the horn and he stopped backing up. I had enough room with my tiny car (Toyota Echo at the time) to scoot around him. Last I saw him, he was back to backing up, but this time with the traffic from the green light behind him heading toward him. Hope he didn't hit any of them!