My feeling is, if a dog is that hard up to break free, let it go. It's like a boyfriend who wants to break up. We all know the old adage "If you set someone free, and he never comes back, then he was never yours." I understand the main fear with setting dogs loose is they could get hit by a car, but so could an ex boyfriend. That's just a chance you have to take.
Are You There, Vodka? It's Me, Chelsea (ed. Simon and Schuster, 2009) - ISBN: 9781416596363