My wife, when she regularly walked into work, and had to cross a number of busy crosswalks got into the habit of smacking cars with her open palm if they passed too close. Her argument was that if they were coming close enough for her to reach them, then they deserved the smack. I didn't agree, for the obvious safety reasons, but also whenever I was walking with her and she pulled this stunt the male drivers who would never strike my wife didn't seem to have the same qualms about coming after me. Though I guess it is the eternal cycling ped. question. How is it a driver who is in such a hurry as to risk someone else's life will suddenly have all the time in the world to pick a fight when you yell or give them the finger. I agree with LordOpie, its better to wait until someone comes to a complete stop. No matter how right you are the person doing the yelling always looks like the Jackass.