Development of evaluation criteria for curve-section safety level with visual distortions on two-lane rural highways

Curve-section traffic accidents occur due to a mixture of vehicle, human, and road environmental factors. Traffic safety research in curve sections, however, so far has been confined to only investigating the effect of highway geometry factors on traffic accidents. Accordingly, this study suggested curved part safety-level evaluation criteria by complexly considering the hazard-level, which forecasts traffic accidents utilizing geometric structure of road, and the level of visual distortion, which recognizes the geometric structure of road as different from actual. The research first presents data collected on the geometry of highways in curve sections and from field investigations of traffic accidents. Second, a rating scale for curve-section safety level is presented with a consideration of hazard levels and visual distortion as variables. Third, evaluation criteria are presented for curve-section safety level, utilizing a safety-level rating scale. The evaluation criteria are classified into three levels dependent on route alignment type and each level is again classified into six grades from A to F. In this research, the causes of accidents can be determined in advance during design of the curve sections of a highway by applying evaluation criteria for the safety level as the curve sections are developed, and thus can be utilized in selecting a priority order for projects when implementing improvements in existing roads.