Fence! Again, FENCE! We have two pomeranians, who cannot be seen once they are within 10 feet of a car. T posts, and rabbit wire make it go really fast, and then you needn't worry again. Our dogs run, chase balls, and are walked daily. MILES of walking. And they still think they can take on your average truck. Go for the fence. Loose dogs are generally trouble unless closely supervised. (speaking as a former sheep rancher)