Methods of multicriteria decision analysis within the road projects like an element of the sustainability

The present communication is based on the research undertaken by the author and whose principal results are detailed in its thesis entitled « Choice of alternatives of road infrastructures : multicriteria methods » like on the prospects offered by this one. The problems of the choice between various alternatives are permanent and crucial in the projects of systems of transport and road infrastructures. The designer who works out a technical solution must have objective and global methods in order to propose to the decision makers, who are generally a political entity, an optimal alternative. The complexity of the many fields affected by the transport infrastructure as well as the diversity of the various intervening actors directly or indirectly in the study process are as much elements to integrate in this choice. Only methods of multicriteria decision analysis, associated with a dialogue integrated into all the stages of the study process, make it possible to the designer as well as possible to take account of this complexity. The use of such methods also makes it possible to bind the objective aspects of the choices, based in particular on technical evaluation of the performance indicators of the alternatives for each criterion, with its subjective aspects which are the relative consideration of importance of each criterion, also called weighting. These methods of multicriteria decision analysis used in parallel with dialogue methods are clearly at the basis of a study process ensuring the realization of a sustainability road. They indeed make it possible to bind social, by the dialogue of the various actors, economic and environmental dimensions by the consideration of adequate criteria. Moreover, the consideration of the needs for the future generations, by the taking into account of the cycle of life of the infrastructure, is easy to realize. The author carried out an actualization of methodology of the road project process while basing him on the integration of these principles in the procedure. An evaluation of the various methods of multicriteria decision analysis was carried out and tested on a real case in Switzerland. It results the following main clauses from them : The use of the method of partial aggregation Electre III makes it possible to better moderate the judgments and use easy indicators; The honest separation in the stages of the process of the phase of weighting, which is to be realized before the alternatives generation, this one preceding the phase of the evaluation of the criteria; The objective judgment is to be realized by the designer and subjective weighting by the decision makers.