Severity Indices as measurement tools for road safety in mountainous highway sections: case study of the Centinela–La Rumorosa highway

The evaluation of road safety in highway infrastructure requires tools that enable the objective identification and prioritization of risk conditions. This study proposes the development of Severity Indices (SI), a quantitative tool designed to assess the severity level of road segments based on geometric and safety-related variables. Unlike traditional approaches based on qualitative audits, the SI allows for the establishment of severity levels through the integration of measurable and reproducible data. The guiding research question is: How can an index be constructed to quantify the level of road risk based on the physical characteristics of the road and their relationship to crash incidence? To validate the methodology, it was applied to the Centinela–La Rumorosa Highway in Baja California, Mexico—a roadway with high geometric complexity. Variables such as curvature, slope, superelevation, signage, and containment devices were analyzed and correlated with crash records using statistical and spatial analysis in Minitab version 21.1.0. A total of 35 critical points were identified in the descending direction and 28 in the ascending direction, to which SI values were assigned. The results show that this tool allows road safety assessments to be transformed into quantifiable, comparable, and technically informed decision-making processes. The development of the Severity Indices represents a significant methodological contribution to improving road safety evaluation, particularly in contexts where it is necessary to prioritize interventions based on evidence and consistent technical criteria.