But is following a Road Rager a smart thing to do, risk wise? Even if one is trying to get info to the police? Especially on a motorcycle, where one usually needs more than one hand to safely operate the controls!
Consider the "DR ABC" that is often taught for first aid. The first part of that is "Danger"- that you don't add to the number of casualties by becoming one yourself.
In the area of personal protection, there's a similar principle at work- Don't take on unneeded risk. If the situation is bad enough that you need law enforcement, it's probably also bad enough that you need to get away from it.