Originally Posted by
HIPCHIP
If someone physically harasses you, or does something illegal with their driving, if you can identify them, then you can make a citizens arrest. So if you have a plate, the description of the car, and saw the driver, you can have them prosecuted. Of course this also means you will probably have to take time to go to court and testify, but it can be done.
"Citizens arrests" are heavily jurisdiction dependent. Make sure you know the law before attempting such a thing. To the best of my knowledge, here you are allowed to detain someone only for criminal code violations, not civil violations, and only while they are committing it. If you see the same person at a later time, or try to "arrest" somebody for a traffic violation, detaining them can earn you a criminal charge (kidnapping), and a civil suit (false imprisonment and, since you probably had to use some physical force to detain them, assault).