Actually, no there aren't. Unless you can stop in a well lit area with other people, the more the better, you are better off continuing on while dialing 911 to report the make, model and license of the vehicle harassing you. Honking your horn and turning on your flashers to attract the attention of other drivers (and spur additional 911 calls) is also a good idea.
Confrontation is the more dangerous situation. A pissing match with a total stranger on an on ramp is always stupid. Unless you're a comic book super hero, nothing good will come of it.
If the aggressor pulled off, I would keep on going.
When the aggressor remains on the road, I pull off.
Remaining on the road with a person who is trying to provoke an accident is a terrible idea.