I don't notify my own insurance company if the other party is clearly at fault and there is a police report that reflects that. Your insurance company will record the incident and it counts against you. (They SAY it doesn't count against you, but it does. They track the number of incidents you are in and even not at fault accidents count against you to a certain degree).

This is a scenario where those who aren't as experienced in dealing with insurance should probably get their own company involved, however.

edit I guess the downvoters are confused about how insurance works?