I was walking my mum's dog off-leash on a road, and another dog ran to attack her. That dog ignored me until I voiced a great big growl: at which it suddenly noticed me for the first time, and stopped. You're bigger than them. You have a right to be on the road. They'd have to be crazy to attack you.

In the city (in parks and on cycle trails) when off-leash dogs approach me, I slow down to avoid any risk of hitting them (as with children).