I've had a lot of experience with untethered dogs since I lived in a rural area for years. They are territorial, they see you as a threat and want to protect their territory. Keep going, once you pass their boundaries (usually the edge of their yard) they consider it a success and quit. There are exceptions,but that has worked reliably for 40 years. The only dog ever able to catch me (tore my pants) was a dachshound, I was going 20 mph when he caught me. Don't assume you can out run a small dog, just keep going,you're safer on the bike than getting off in their perceived territory.

Marc