If the person is harassing you or being loud or interfering with traffic, the police may be able to charge him with disorderly conduct or some other minor offense. I have a friend who has told me that recently a man has been following her. He sits in the car and watches her, follows her when she is in her car or sits in front of her house when she is inside. We receive many inquiries about this type of behavior. It is illegal and potentially dangerous.
Most states have laws against stalking.
Get as complete a description of the guy as possible and notify the police. This behavior is dangerous and needs to be stopped before it escalates into something more serious. What is worse is that this type of behavior is not isolated and singular. Many stalkers have a long history of this behavior. The police should be very interested in finding out about this guy.