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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 Vss of two consecutive and independent geometrical elements of the road. [ABSTRACT FROM AUTHOR]

Crash data in the USA show that approximately 47 percent of fatal crashes occur at night. Sight distance is severely reduced at nighttime as it compares to that in the day often resulting in problematic situations. Horizontal alignment can compound this issue, since most drivers would not be able to see far in advance to recognize the sharpness of the curve and adjust their speed accordingly: a process that they can complete at daylight conditions. This study attempts to understand the influence of roadway geometry and especially curvature on nighttime crashes and presents a preliminary analysis of this issue aiming to identify the magnitude of the problem and provide some guidance for future research. The findings indicate that there is indeed an increased crash occurrence at night and this is related to the curve radius. Sharper curves, i.e., curves with small radii, showed an increase in crashes and crash rate when they were compared to their corresponding daytime crashes. Design consistency was also examined by considering the radii of successive curves. The data again points to the differences in crash experience when considering the relation between two successive curves. Additional work is needed to further explore these issues and develop more statistically robust models for refining the nomographs developed here. [ABSTRACT FROM AUTHOR]