A lot of good advice here. The reason the flag/hankerchief trick works is their eyesight is amazing but they're stupid as a stump. I've had to literally get out of my car wave my arms and yell from 10ft away to get them off of the road in front of me! I think they didn't realize I was a human while I was in the car.
Gaily bedight, A gallant knight In sunshine and in shadow, Had journeyed long, Singing a song, In search of El Dorado