Chasing cars has nothing to do with dominance. My guess is that you never had a dog that's crazy about chasing cars, because if you had you'd know that a touch wouldn't help.

My first dog was a Swedish Lapphund that used to chase cars. She only did it when she was off the lead, so there was no chance to physically punish her. Once my father actually hit her with the car on purpose (just enough to hurt a little, but not injure the dog) but it didn't help at all.

My third dog was a Belgian Sheperd Tervueren and she was completely crazy around cars. She was 1,5 when I got her and had already established the behaviour. If she got loose near traffic she'd chase the cars and if possible bite the tires. I tried everything, even very hard physical corrections, but nothing helped; she was totally blocked around cars. She never stopped chasing cars (altough, she might have stopped had she become older than 2 years old- and no, she wasn't run over by a car )

The collie cross I have now wasn't chasing cars, only trucks and buses. I taught him not to by rewarding a different behaviour rather than punishing chasing trucks/buses. Away from traffic I taught him to look a me to get a treat. Then I used the command to look at me whenever I saw a truck or bus approaching. If he then looked at me I gave him a treat. If he didn't I ignored him (with a firm grip on the lead). After a while he had learned that he was rewarded if he didn't lunge at the trucks and buses and now he's completely stopped chasing them.

It's also important to learn to see the signs in your dog. Dogs have signs that tell that they are getting excited and if you learn to see those signs you can stop your dog before she starts chasing the car, which is much better than to try to punish her while chasing cars.