I am a dog owner and I wish there could be clearly defined areas. Mine is generally good off lead and does come back, but NOT 100%. I don't think he ever will be. He is a labrador, has not got a bad bone in his body, but wants to play. However, not everyone knows that!
I try to let him off lead in places where no one else is around, or a regular dog walking route, and put him back on lead as soon as I see another person. This, however, is not foolproof, I don't have eyes in the back of my head and I just don't expect mum, dad and toddler kicking a football in the middle of an overgrown field..... Dog did though, and decided to join in. Luckily, on this occasion, no harm done, mum and dad had child stroking dog and playing with him, but it would make my life a lot easier if some areas were recognised dog walking areas.
The is one that we sometimes travel to, a proper dog park with obstacles etc., that is brilliant. There need to be more, because, as a dog lover, I can really sympathise with those who are not, and don't want random dogs barrelling up to them.