An accident is an event of fortuitous nature. It can reach with the integrity of people, properties or environment. An accident can be a minor or major, in the first case we call it incidental, but if it is really serious it can be a catastrophe.

The road accidents are among most current, transport is a sector where the accidents are often serious, particularly with the transports of mass like plane or train. Sometimes it is the transported goods which involve a risk (oil, chemicals?) and can provoke accidents like the oil slicks.

Most of the time, the accidents lead to the development of new payments, laws, protection prevention, the shock caused by the accident often make people to react. The man's hand is often the origin of an accident, but in certain cases they are the machines, tools, means of transport used which are prone to failures...The nuclear accidents like Tchernobyl in Ukraine in 1986 take part to this category. The most serious accidents, like catastrophes, are caused by mother nature. Tsunamis, earthquakes, floods, cyclones, hurricanes, all these natural phenomena have heavy consequences on humanity. Sometimes theses natural phenomenons are amplified by man's actions.