These dragons are ranked by the DDLA as safety level 1. This means that these dragons do not attack humans unless they receive very heavy provocation, and usually fail to deliver major injuries even when this happens. In short, they pose close to no threat at all.
Dragons in this category are mostly species who are not adapted to fight and survive by avoiding battle, or living in places without natural predators. However, some (like the cerberus dragon) are just very cowardly at heart.