Here in England, you are not required to inform the police of an accident unless:

* Somebody was injured
* You caused damage to a car or any property, or you injured an animal, and you can't locate the owner, having made a reasonable attempt.
* The other driver(s) refuse to give you their details.

You are required by law to stop at the scene of an accident that you're involved in, and you must provide anyone affected by the accident with:

* Your name, address and the car registration
* Name and address of the car owner, if it's not you.
* Your Insurance details.

One more thing which hasn't already been mentioned (Which may only apply in England)- You should never admit liability following an accident as many insurance companies state that your insurance will be invalid if you do.

Unfortunately I don't know much about the laws in other countries, but I do know that in Germany they have a Good Samaritan Law which makes it a legal requirement for the first person to arrive at the scene of an accident, to help people who may be stuck or injured and to call emergency services where required.

I've only been involved in one accident which I consider to be moderately serious, and at least fifty cars must have passed us, including one police car (It was rush hour) before someone (in a big 4x4) actually stopped to help us tow the two cars out of the path of oncoming traffic and then let us use their mobile phone to arrange for the cars to be towed away...