Why don't some cyclists signal that they're about to pass? I frequently ride a well-known, multi-use trail in the DC area, recreationally and now as a commuter (awesome-I don't know why I didn't do it sooner) and am always stunned by how many "professional looking" cyclists zip past me without any kind of warning. Yesterday, on my trip home, a guy passed by me on the right side (left is much more typical) just as I was about to make a right turn in an intersection. He didn't signal and showed absolutely no response (typical) at all when I yelled at him. I almost turned into him but luckily responded quickly enough to miss him by a few inches. Had I not reacted so quickly we would have both wrecked out in the intersection during a busy rush hour. A simple "on your right", or preferrably "on your left" would have prevented what would have caused a near-certain accident. In addition, I always signal my intention to pass to everyone. My questions are: why do many experienced riders not signal when in a multi-user environment and, what is the appropriate response?