This is used when children are misbehaving in the car. A parent will threaten the children with the phrase, "I'll turn this car around right now!" so that the children will stop behaving in a bad manner. Normally, this statement is used when the children are going somewhere that they are excited about, such as a playground or another fun activity. Turning the car around means that the parent will turn the car around to return home and there will be no fun that day. Does this answer your question?