Studies of the concentration of traffic accidents in Japan show that about half of all accidents causing casualties on arterial roads occur on about 6% of their total simple road sections and at about 4% of all intersections. Although traffic accidents are caused by complex combinations of three factors, human beings, vehicles, and roads, human factors are the most common causes of accidents. However, the existence of hazardous spots shows that the contribution of road factors to accidents at these locations is greater than elsewhere. Under the criteria for the geometrical design of roads, the minimum values for elements such as horizontal alignment, vertical alignment etc. are set according to the design speed, and although there are basic concepts concerning desirable combinations and undesirable combinations of the horizontal alignment and the vertical alignment, there are few detailed regulations such as the combination of numerical values. Roads have a three-dimensional alignment created by combining the horizontal alignment and the vertical alignment, and at the same time intersections are located at intervals along their length. Therefore, to accurately evaluate the safety of a road, it is necessary to treat it as a space that has a three-dimensional alignment and a certain length. From this perspective, an accident data base was used to perform an analysis to clarify the conditions of road structures where traffic accidents occur easily. This report presents the results of such analysis of the safety of a road from the perspective of space with three-dimensional alignment and length, and it advocates the view that to truly improve road safety, it is important to not only provide design standards for individual structural elements, horizontal alignment, vertical alignment etc., but to also give full consideration to combining these elements. For the covering abstract see ITRD E135448.
Abstract