Following up on an earlier post "how do you communicate with people who are acting badly?", my girlfriend came up with the best candidate so far: Whoa!
Whoa! According to web definitions this is commonly used for a draft animal to stop; or to cease or slow a course of action. With some road users the draft animal that comes to mind is jack ass: A male ass or donkey; a foolish or stupid person.
So, let me know what you think about yelling whoa every time you see bad behavior. It's growing on me.