When you have an accident, there are, firstly, the legal formalities (手续) of exchanging names and addresses with others involved in the accident and informing the police. However, you are required by law to stop after an accident only if: 1. Somebody other than yourself in or outside your car has been injured. 2. A vehicle not your own has been damaged. 3. Any horse, cow, sheep, or dog has been injured. Furthermore, the driver himself must wait at the scene; it is not enough for him to leave his friends to attend to the boring formalities while he goes off on more important business. If you have been involved in an accident and have stopped, you must give your name, address, and licence number to anyone who has a good reason for requesting it. If somebody is injured, the driver must produce his insurance document on request. If these formalities are followed it is not necessary to wait for the arrival of the police. It is, however, often wise to do so. Although the police are expert at drawing plans, taking measurements and photographs and gathering other evidence, you yourself might want to point out certain features of the accident to the police.