until your dog has been properly trained, do not let him run off leash even for a minute! Dogs aren't smart enough to look both ways before crossing the street. They have no idea that cars can kill them. Accidents happen in the briefest of moments and it only takes one mistake to lose your dog forever. If you love him, put his safety first and keep him on his lead!

i would say make it a game ..play hide and seek with him in the house or in a place where its safe then act like he's done the greatest thing in the whole world when hes found you ! Hug him, praise him, pet him, love him and reward him with treats.

hope this helps ..