Sometimes you don't even see them coming: the one that took me out in 2019 I didn't see as I was watching in my glasses-mounted mirror looking for traffic behind me when it crashed into my BB from across the road. I was doing 40 km/h (25 mph) and accelerating. The dog had run parallel to me in the field across the road, and was able to cut out a driveway, cross the road and plow into me. No idea what the dog's intentions were (playful or violent) but the resulting injury to me was the same either way.
I couldn't have out-run that dog had seen it and tried.
I'm just glad that I was going "only" 40 km/h and not the 60 I was working towards when I hit the pavement.