My neighbor's dog taught my dog, Ebony, how to herd the UPS truck. I thought that was just something border collies think up.
I learned why dogs chase cars; They are either playing a game or they are hunting. To a greater or lesser degree, chasing involves a dog's natural prey drive.
In most socialized, well-adjusted dogs, prey drive expresses itself as a canine tag game, in which the dogs take turns being "it." The object isn't necessarily to catch the other dog; the real fun is just running around. Chasing balls or Frisbees is another outlet for dogs' prey drive.
Dogs may play-fight as part of the game of tag, lunging or even snapping playfully at one another during the chase. This form of play may extend to include cats, joggers, people riding on bicycles or skateboards, or cars. The intent is not to hurt or kill, but to engage the other creature (or thing) in a game.
A good training tool for chasing cars is an electronic training collar;