Is it always the same dog? If so, see if you can befriend it. Say "Come on! Let's go!" While I have never been chased by an aggressive dog (and I know they're out there), I have raced a few. And they always win the sprint. I'd rather have it be a friendly race than a race with a bite at the end. They can put on an amazing burst of short-term speed. Not sure of their top end, but pretty sure it's higher than mine.

My philosophy as regards dogs is this: they are instinctual pack animals with a strict hierarchy. They want to know where they fall in the pack; and are, of course, instinctively mistrustful of members of other "packs" (which includes us). Let the dog know, right away, your position in the pack. And that position is... above his/hers. If you don't want that dog bothering/following/chasing you, say so, loudly, firmly (and don't let your voice crack while commanding "No. Go home!")

This will sound like a cliche, but don't show fear. If you show fear, you are inferior, and they can take you down (look it up... it's in the rule book... unless, of course, you're a puppy, then that's against the rules... "Not allowed to hurt the puppies"... but human adults are never "puppies"... kids are sometimes, but not necessarily).

If a dog attacks, get something (like your bike) between you and it, hopefully until it loses interest or someone arrives to help. As much as I love dogs (I've grown up around dogs, and have three now), I've made a determination to myself that if I ever have to fend off an attacking dog, I will hurt it, as badly as possible. If it's attacking me, it's because one or the other of us has violated the rules. Once someone breaks the rules, it's gonna be a fight.

Having spouted all my brave rhetoric, I have to admit to quailing inwardly when I pass a Rottweiler ("Please, please, please, doggy, stay inside the fence. Don't eat me."). So far, they've all stayed inside the fence. Here's a corollary to The Rules: Don't Mess With A Rottweiler (or any other aggressive breed). I think that the aggressive breeds also operate under the same rules of behavior of the other other dogs, with the exception that they'll break them sooner, and once they clamp on, they won't let go.

Whew! I think I'll go home and play with my Golden Retrievers now.

Lin