This paper is based on research of the authors emphasizing traffic safety and highway geometric design, which has led to the development of three quantitative safety criteria for distinguishing sound and poor design practices on both planned and existing two-lane roadway sections. The safety criteria are directed toward the achievement of - design consistency (Safety Criterion I), - operating speed consistency (Safety Criterion II), and - driving dynamic consistency (Safety Criterion III) in highway design. All three criteria are evaluated in terms of three ranges, described as "Good", "Fair" and "Poor". Cut-off values between the three ranges are developed. Furthermore, it is dealt with the issues: design speed, operating speed, and sound friction factors. A comparative analysis of the actual accident situation with the results of the Safety Criteria reveals a convincing agreement. It is known, that signs and markings can improve the safety record of a road section. However, the improvement is seldom substantial and certainly not to the level of transforming a "poor" design to a "good" design. The developed safety evaluation process is meeting with acceptance in the professional highway engineering community. It has been adopted or referenced in their geometric design guidelines by several Roads Agencies internationally including those in Canada, Greece, Hungary, Italy, Japan, South Africa, and partially in the United States. It is thus reasonable to suggest that the methodology has gained international acceptance. Thirty case studies were analyzed. The results confirm that the classification system agrees well with the outcome of large accident databases. For the covering abstract see ITRD E135448.
Abstract