A major difference between the Pacman ghosts as described here, and cars in traffic, is that the ghosts will always be able to smell the pacman, no matter how far he is, and a driver in a car has a limited view on the traffic surrounding him.
The latter (limited) is easier if you use objects for the cars, the former (unlimited) is easier using antiobjects.
You could have tiles forget the scent/roads forget the traffic. With each simulation step, decrease it until it's gone after however long you want it to be remembered. Then, ghosts would have to be somewhat near pacman, and cars are only influenced by what goes on around them, not what happened a while ago.
Of course, simulating the actual view of a driver, i.e., excluding things behind the vehicle etc., takes a lot more work.
The latter (limited) is easier if you use objects for the cars, the former (unlimited) is easier using antiobjects.