You need to post the code for the class which shows how you currently have the actor moving (read the page linked to the 'Posting code? read this.' below the reply box).
Still, not enough information. I asked for the entire class code -- not just the act method. I cannot see how 'isAtEdge' is declared nor what the 'car' method does. Neither can I see any code that moves the actor when not (apparently) at the edge.