i've had several dogs chase me after a loud "NO!" was shouted at them. you know you're in trouble when they don't bark. luckily there was not a headwind that day, because they were gaining on me while i was going 31-32mph for over .5 miles. the only reason i escaped that day is because a truck driver saw what was about to happen and scared them off. this was in rural arkansas, where lots of people think dogs are free to roam and that leash laws are only for city folk.