With this sort of breed its not so much the amount of exercise you do with them but mental stimulation. Try doing trick training, hiding his food so he has to sniff it out that sort of thing. It should calm him down a bit. Look into something like agility when he's older these breeds need a job to do. Try teaching him the watch me command where he focuses on you and give it when he sees a car its the herding thing unfortunately he's trying to herd the cars so the best thing is to try and get his focus onto something else.