German Shepherd dog

Has anyone ever had any luck with stopping your dog from running the fence chasing cars?  I ususally kennel him when I'm not home so he doesn't run himself ragged, but was curious whether anybody had broke a dog from car chasing.  Let me clarify, my dog is not loose, he's in the fence just running the fence when cars go by.

Thanks for the reply.  He is about 3 and a half, but I've only had him for about 6 months, although it seems to be getting worse.  He has never tried to chase anything while on the leash (he's quite submissive), but he does have a high prey drive for things like squirrels, cats, and birds while alone in the yard.

Yes, I would use an e collar. I have a board fence around my yard and have had dogs start this....I put a stop to it quickly. I put the collar on, sit on the porch, and wait. When a car goes by, dog chases car, I tell him no, and if he doesn't immediately stop, he gets a correction. Also, if he learns to not do it when you are there, but wants to do it when you aren't around, you may have to hide in the house and watch him through a window, then correct him if he does it. Then he will learn that it's not allowed at any time. During this training, be sure to be consistent. Make sure to never leave him out for several weeks unless he has the collar on and you can watch and correct him. You can't let him get away with it sometimes and then correct him others. This won't take care of the problem. If you can't watch him all the time til the problem is totally corrected, put him up. Good luck!