Even when there is an obvious threat, something else unexpected may be stalking you too. Consider the case of the rider commuting to work in city traffic who came up a couple in a car who were having such a violent argument that he could hear them shouting through the closed windows from several car lengths away. The passenger was jumping around so violently that the big SUV was rocking, and the driver's reactions to her were making him swerve slightly. They were in the left of three lanes going that direction as the rider overtook them in the middle lane. In the right lane and ahead was another car going about the same speed as the rider. A third car occupied his right rear quarter. As he overtook the arguing couple, the rider shifted his attention left to watch them, so he'd have warning of any sudden change in speed or direction from that quarter. He continued to look as he came abeam, and remembered thinking, "If they don't cool it, there's going to be an accident." It was an accurate prediction, but they weren't involved. As the rider turned his head to the left to watch the couple, that car ahead to his right moved into his lane ahead of him and slowed, apparently in response to a fourth vehicle that was backing down a driveway toward the curb. The rider looked up to see the car immediately and unexpectedly in front of him, its brake lights glowing. He hit his brakes hard, overbraked, and crashed his Kawasaki in the middle of the busy boulevard. The warring couple apparently didn't even notice what transpired just outside the car's passenger door.