The Yellow Dog Project was created to bring awareness to dogs who need space while training, recovering from surgery, or being rehabilitated.
If you see a dog with a YELLOW ribbon, bandanna or similar on the leash or on the dog, this is a dog which needs some space. Please, do not approach this dog or its people with your dog. They are indicating that their dog cannot be close to other dogs. How close is too close? Only the dog or his people know, so maintain distance and give them time to move out of your way.
You can read more here: http://www.yellowdoguk.co.uk/