Back when I roller skated, the ultimate question: you see a person and a dog, several meters apart. Is there a leash between them? :-)

Oof. If yes, you might be about to get nailed. If no, will the dog run after me and bite me?

I’ve had a dog on my heels doing doing 40kmh.

They were at my heel, past the back of my rear tyre. I was briefly a competitive sprint cyclist.

FWIW, it's better to stop and talk to the dog. Dogs don't really want to bite you, most will just chase you and don't really even know why. If you stop and confront them, they are confused and don't know what to do next.

Get off the bike on the side opposite of the dog and keep the bike between you and the dog just in case, if you are afraid.

Nope, I was out of there. This one was a biter.