[Impact Study of Motorway and Railway Plans - Methodological Approach On Forest Vegetation and Hedges]

Since 1985, a law constrains most of the important building and development projects to be controlled by an impact study. But up to now, very few information about methods used to weigh up the impacts existed. We have taken advantage of a research carried out on the effects of T.G.V. plans between the French border and the city of Ath, to settle a method available for some linear basic equipements (road, speedway, railway, channel ...). The effects on the forest vegetation and hedges of such basic equipments have been described in the first part of the paper. Thereafter the impact criteria to be used for each community type are analyzed. With the example of T.G.V., the paper shows the way to compute the global impact for each community in the area of the study.