My dog goes crazy after cars. When I walk him and he sees a car he just starts pulling on the leash trying to chase it. He is better than he was before though,because before whenever a car would go by he'd bark, jump, growl and spin around. So I supose he's a bit better but how can I get him to walk calmly on the leash without pulling and trying to chase the cars? He sort of chases everything that moves though but the cars are my main concern.