I haven't been passed by a runner on the road, but it has happened many times in the dirt, when I'm on the 30 pound bike with several pounds of water and gear. The steeper it gets, the more of an advantage it is for the runner, especially a 140# runner against my total load of 250#. Once, I chased a fireman who was on foot, but he was carrying a radio, water, and heavy clothes and boots. I couldn't catch him until the trail leveled out a little, and he wasn't breathing hard and started a conversation with me.