Red Light

I’m making a little interactive/game thing where you control the traffic lights at a four-way intersection. It works so far, but there is one bug that is driving me crazy. For some reason, the car that comes from the top of the screen can’t be hurt. The other cars avoid it, so I know that they recognize it’s presence. Help would be appreciated. Here is the fla: http://www.steven-s.us/upload/store2/RedLight.fla