Methodology for sectional risk ranking of an existing two-lane rural highway alignment for inspection purposes

The objective of this paper is to create or establish a suitable methodology that exploits the geometric features that characterize the existing infrastructure on two-lane rural highways, regarding the geometric features (horizontal and vertical alignment, superelevation, sight distance) and evaluating the provided road safety level. Through the utilization of these elements, the purpose is the determination of evaluation coefficients that show the hazard level of every road section and the critical regions of the road network, while identifying the crucial curves which have high potential for road accidents. In this context, a hierarchy of critical parameters influencing the hazard rating of a road network was made regarding to geometric design. For each of these parameters, appropriate mathematical rating equations were created, based on the limit values presented in the literature. Initially, each parameter was correlated with the limits set by the geometric design guidelines, while simultaneously the hazard level and the sensitivity of each parameter were defined. By this procedure, appropriate mathematical expressions that estimate the hazard level were developed, and also appropriate weighing coefficients were sought. Thus, a combined rating that characterizes each road section was obtained and the critical curves that present high possibility of accident occurrence were depicted. Finally, data was collected for a significant sample, of about 1000km, of the existing Greek road network in order both the results of the proposed methodology to be evaluated and also these to be compared with the results of the operating speeds V85 of two consecutive and independent geometrical elements of the road.