Different cities and townships have different rules about when you are required by law to call the police after a car accident in PA. Generally, it is necessary for you to call 911 if anyone has been injured, or killed, in the crash. It is also necessary to call 911 if there is significant property damage or if the accident has impacted public safety.
Even if an emergency situation is not present, it is important to move your car to the side of the road and to call the nonemergency police number in the city or town where accident occurred. The police department will need to, at a minimum, take a report of the accident. Police can also tell you if an officer needs to be dispatched to the scene to do a full on site investigation.
If you have any doubt about what to do after a car accident then it is important to call 911 and let the dispatcher help you so that you can make sure that you comply with the rules in your jurisdiction.