Abstract
In the analysis of risks of a certain activity, f.i. dangerous materials, two elements are considered generally (1) the consequences of an accident during the activity, e.g. how big is the economic damage, how many injuries etc. (2) the chance of such an accident and /or the chance on the different accident developments, f.i. the chance that dangerous freight is get off at an accident and the chance for an ignition of an explosive gas. In particular the element of chance in risks is described here.