While the excavations at Étiolles are “planned excavations”, the majority of archaeological research in France today is preventive, with the prevention of destruction in mind. Unplanned rescue excavations are no longer carried out. Since 1992, when European countries signed a convention for the protection of archaeological heritage, sondages are used from the impact study stage (see diagnostic) which precedes large-scale developments affecting the subsoil. The archaeological potential of a site is evaluated using trenches. If significant finds are made, the ministry can order a short excavation, added to the budget of the development project. As there is only a short time during which archaeological work may take place, highly effective teams from the relevant public bodies, such as the INRAP, the relevant departments of certain local authorities, and private companies approved by the administration, are required.