When a dog is in "prey" drive saying anything to the dog is probably pretty
useless. Yelling will always kick the dog into higher prey drive which is
why screaming at barking dogs is so ineffective. Now using something like
telling the dog to stay or you git home as they are coming towards you but
not in a full out run can help. I've told dogs in a deep, mean sounding
voice to GIT HOME NOW, not yelled but threatening and 99% of them stop and
don't advance. I just came from the older lady's home where I evaluated the
dog. She's having all kinds of problems and one of the was loose dogs
approaching her when she was walking her dog. Now she's carrying a small
water bottle that she hooks to her pants loop. We got a chance to try my
suggestion out on the walk and it worked beautifully.

If I was on a bike I
would take my water bottle and blast the dog in the face with a nasty GIT
HOME voice