Excuse me!, my son was bitten on the arm by a unleashed dog pushing his bicycle past a dog walker on the footpath in a similar situation and afterwards became terrified of dogs. The way I got him over his fear was using the leash as an indicator that he had the choice to easily avoid the dog and that a leashed dog couldn't get him. The leashed dog was the first step in his fear rehabilitation to give him confidence that the dog being leashed did provide him with choices to feel safe around them. The basis of his early treatment was to ensure that a leashed dog posed no threat beacause they were restrained and he had the choice to pass them at a distance he felt safe knowing that the dog couldn't make physical contact with him. We could have given him the above advice I highlighted, but I doubt such advice although I agree should be the case in a perfect world, would have had much effect in his dog fear rehabilitation.