Chains of causalities of environmental impacts

In order to prepare an encompassing ex-ante assessment of the impacts of the transport system on the environment by building impact indicators, the pressure-state-impact concept is widen into the concept of chain of causalities or process. A process is defined by an output of the transport system, a homogeneous series of physical, chemical, biological, psychological relationships between elements, and a final target. All the known today impacts of the transport system on the environment are described as a list of 43 chains of causalities. The knowledge of the relationships will be used to design indicators or to know what does and not does measure a given indicator. Key-words: environmental impact, classification, process, chain of causalities, transport. 1