I've had several dogs over the past 30 yrs and the retarded one here now (13 month old German Shepherd mix) is the first one I've used a shock collar on. 

I should have used one on at least 3 other dogs and they might have lived longer. 

I only shocked this dog maybe 8 - 10 times total over the course of 3-4 weeks at the beginning of this summer and he hasn't chased cars on the road since.  Will still run along my vehicle when I come in the drive and will sometimes chase me to the edge of the yard when I'm leaving, but has no desire to chase strange vehicles in the road.   

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The shock collar is a miracle worker.  Just don't go overboard with the shocks, and remember it's a tool, not a punishment.   Use it at the beginning of the 'chase', not in mid chase or full on car chase mode.  Shock the impulse to chase, not the chase.  You can tell when their mind is gearing up and readying for the car to get 'here',  wait until 'here' is just ready to start (attention on coming vehicle, but hasn't made the move yet toward the road -- if you've watched the dog much, you can tell when he is just ready to spring into chase mode) and 'zap' HARD and short. 

It won't take too many times, the hardest part is the vehicles sneak by when the humans don't notice.  If you can, train yourself to start noticing approaching vehicles earlier, you need to be ready before the dog is running towards the road. 

Also to stop the dog from jumping on people, step on his back feet when his front paws are up.  No shocking is required, but everyone needs to be on board with this, and the learning curve will be short and sweet.