Letting your dog out the door, for instance, is not normally considered reasonable control. A dog that is leashed or under your control as you walk him is considered reasonable. You can be held responsible for damages which your dog causes to property or persons. As a courtesy to others and to protect your dog. Dogs are no match for cars.
Dogs running at large are at serious risk to themselves as well as to others.
It is the reponsibility of the dog owner to control their dog at all times. By the time your dog is 3-4 months of age. It's wise to follow the advise of your veterinarian in this area. Depending upon which vaccine your vet uses, you will need new shots every one or three years. The answer to this is simple.