Interaction between Rockfalls and Vehicles Studied for Speed Limit Zonation along Mountainous Roads

Abstract

A rockfall risk assessment along the transportation route to a historical village is presented herein with the aim of evaluating the potential of this approach for speed limit zonation. Mountainous roads are often subject to rockfalls, which should be taken into account for territorial management and planning, especially when dealing with dynamic variables, such as vehicular traffic. Rockfall risk analysis along roads is often aimed at assessing a risk value to plan or prioritize mitigation purposes. Nevertheless, such approaches can also be used to regulate traffic in terms of posted speed limits. Traffic is, indeed, a key variable in rockfall risk analysis due to the spatial and temporal correspondence that a vehicle can have with an either falling or fallen rock block. In order to address this relationship for speed limit zonation purposes, in this paper, a semi-quantitative Rockfall Hazard Rating System was applied to a mountainous road leading to a popular tourist destination in eastern Sicily (Italy), which is characterized by winding paths. This approach, which was chosen for its feasibility and international diffusion, was repeated by taking five different vehicle speed scenarios into account, thus providing an innovative application of the procedure in terms of aims and practical results. The achieved outcomes were used to draft thematic maps, as well as to define a suitable speed limit zonation related to the rockfall risk, highlighting that the road visibility strongly affects the final results. The achieved outcomes demonstrate how a scientific approach can be turned into a practical tool of broad utility, especially in mountainous settings, where winding roads and rockfall problems often condition the viability.