I have heard the butter on paw theory as the cat licks his paws and gets the scent of home and knows where to return to, but as to safety tips, I am afraid that the cat will possibly roam around, and if you live in a busy area, you do have to think about the possibility of him getting run over. Is he neutered? if you are really so worried, why not let him just have the run of the garden on a harness/flexi lead. I am afraid it is what my father has had to resort to as his cat has already been run over and still insists on sitting under the cars and fighting with the other cats across the road.