Also, if you have time, maybe sit outside(this will take a while) and everytime a car drives by give him some high quality stinky soft treats(something he would never get on a regular basis) to let him know "yea that car looks tempting, but hey these soft treats are darn good!" Eventually he should look to you, or your mother, everytime a car drives by expecting the treat. Again, this will take some time and patience, but if you do it frequent and keep doing it he won't need to chase the car.