Dogs on the street should be on a leash, where it only for the reason to prevent them getting hit by a car, when they try to run off to the other side of the street when they see something of interest over there.
That said, I've never been bitten by a dog, and have been around them much of my life. My parents used to breed dogs, of many races. I think I can count all unfriendly dogs I ever encountered on the fingers of one hand. And even they were not unfriendly enough to even try to bite me.