Use of multi-criteria model to compare devices for the protection of roads against rockfall

Many kilometers of roads in mountainside areas have adjacent rock slopes that are prone to rockfall. The analysis of these instabilities is a complex and multidimensional process that requires engineering judgments regarding the choice of a suitable protection device because different alternatives can be used to solve the same problem, taking into account the costs and impact on the environment. Nevertheless, very few tools are available to help designers and decision makers to manage this problem by comparing the various alternatives and by quantifying the advantages or disadvantages of each. For this reason it is important to highlight that the Multi-Criteria Analysis approach, as applied in the Analytic Hierarchy Process technique, is a suitable tool since it considers the various aspects that are involved in the assessment and design of rockfall protection devices. The model presented in this article considers the five most relevant aspects (economic, environmental, design, transport, and social) considered in the process of decision making concerning the choice of a rockfall protection device. Finally, the developed model is applied to a real case of a mountain road that is prone to rockfall phenomena, and the results are presented and discussed.