Methodology for Risk Ranking of At-Grade Intersections on Existing Rural Two-Lane Highways

The objective of this paper is the creation of a suitable methodology capable of deploying elements that characterize the existing infrastructure on rural two-lane highways regarding the location and geometric features of intersections and evaluating the built-in road safety. The target is the utilization of these elements to lead to evaluation coefficients that show the hazard level of every intersection and every road section, highlighting the intersections of the road network with reduced safety level. In this context, a hierarchy of critical parameters influencing the risk of an intersection was made, along with appropriate mathematical equations based on the current regulations and corresponding crash reduction factors (CRFs) that have been presented in the literature. Initially, case studies were conducted, and special diagrams were produced to assess the hazard level of each parameter. Then, basic statistical analysis of the results was made using regression factors to develop an appropriate mathematical model for the estimation of the hazard level. A corresponding procedure was performed for each parameter separately, and appropriate coefficients were sought. These coefficients were summed up, and a total score characterizing each intersection has been calculated, leading to a ranking in respect with the hazard level. Finally, data were collected on a significant sample of the existing road network of Greece, about 1,000 km of road network with more than 4,000 intersections (unpaved road intersections are also included), in order to evaluate the results of the proposed methodology. Part of the results has been interpreted with real accident data collected from the police department, showing that there is a correlation between them. This correlation must be confirmed in further research by a statistical analysis between the results of the present methodology and the actual recorded accidents.