IT IS ILLEGAL IF YOU CAUSED THE ACCIDENT OR IF YOU ARE DIRECTLY RESPONSIBLE FOR THE PERSON OR PERSONS INJURED IN THE ACCIDENT, SUCH AS A PARENT, WIFE, HUSBAND, IMMEDIATE FAMILY MEMBER. A PERSON IS...
It varies from jurisdiction to jurisdiction according to a fee schedule established by that particular state's DMV. It is called "Hit and Run" in some areas or "Leaving After Colliding" in others....
This simply means that if you were involved in any type of accident and leave before authorities arrive, you have left the scene of an accident with out making a statement.