Advantages of a comprehensive risk analysis in road engineering.

New and difficult tasks in highway design such as realignment or upgrading of existing or evaluation of different alternatives for the construction of new roads have created a need for disaggregated information about the safety level of the projects in question. This information cannot be gained in the conventional way mainly based onthe technique of accident analysis because of its fundamental methodological deficits. Risk analyses - already well-known from other technical fields - appear to be a possible resolution to this information deficit. This paper summarized the results of a research study carried out from 1986 through 1987 at the Technical University of Darmstadt. The aim of the study was to find out whether risk analyses can be successfully applied in traffic safety research. The method is already well-known from its wide use in the field of design of nuclear power plants and chemical factories. Because of the different type of application, it was necessary nevertheless to adapt the method for the use in a completely new field. Although there are quite a number of elements and procedural details that require to be changed or added, the study has proved the feasibility and usefulness of the application of risk analyses in traffic safety research. The main advantages which can be expected from the use of risk analyses are the following: it requires teamwork of different research groups from various branches of science and thus promotes interdisciplinary cooperation. The knowledge acquired may be refined and extended gradually and in sections according to the necessity of additional information and the research team's capabilities. The method supports immediate derivation of cause-effect relationships, in order to explain the reasons of single accidents. Above all it renders possible quantitative evaluation of different design alternatives for a given problem. The address proposed will present the basic ideas and the main principles of the new method and demonstrate its application by a practical example.