I'm yet to find pepper spray, dog-repellent, sub-machine guns or anything else necessary. Most people don't realise that:
1. If you stop, the dog will usually lose interest in the chase anyway, and
2. Most of the dogs I have encountered have been friendly. Those that weren't were intimidated by me picking up my bike as though it was a weapon.
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I am clinically insane. I am proud of it.
That is all.