Modeling safety situation of level crossings using risk engineering techniques

Safety is one of the most important issues of transportation systems, and new technologies and complex systems increased the need for a systematic approach. Safety matters have a vital influence on railway transportation, and interacting of factors such as manpower, electric and electronic devices, mechanical faces of locomotives and trains, civil engineering issues in the infrastructure, etc. all make a framework of uncertainty. Level crossing, the most dangerous place of the railway system, has a more complex condition, because it is covered by different type of people: The employees and the public. The second group makes it much more complex, because the factor is out of railway authorities control and they really face to the danger. As it clearly could be understood, assessing safety in this situation is a real hard work, because it is needed to manage issues with different roots in a single framework and synchronization of these factors is not a simple work. This introduction implies the necessity and importance of a criteria and framework which could manage the safety issues in such different faces.Risk, as a simple, easy to understand, strong and adequate criteria, could help us to assess safety issues in different places with a single method. Risk has a double hinges those shown undesirable event happens with witch frequency and witch severity. Therefore, in this research risk was selected as a decision criteria and a framework of tolerable rates was fitted to it. The tolerable rates show risk according witch conditions will be accepted or denied. Lack of national framework for this subject forced research team to determine a local framework for RAI.The second phase of research was designing and generating set of steps and diagrams which as a chain leads to assess the risks in the scope of study. The first step of the process, hazard identification in fact is a process of identifying, predetermining of frequency and severity, and rating at end separating the high rated hazards for further studies. The second phase of this process is causal analysis that includes recognizing roots of the hazard, deceiving their frequency of happiness, determining the chain of their relationship, and at end assessing the hazard occurrence likelihood. Consequence analysis, the third phase of research, is modeling and determining the scenarios which will be happened if the hazard really occurred. The output of this phase is set of consequences and their possibilities ratio. Now is the time for assessing the estimated loss in each kind of scenarios and aggregating them with regards to their possibility ratios which are assessed in the 3rd. phase. At the end of this phase, the risk is assessed and should be compared with tolerable rates. If it is not acceptable, risk mitigation process should be applied. Risk mitigation process will be used for unacceptable risks and its purpose is reducing or eliminating risk sources or decreasing their undesirable consequences. This phase includes two main steps: Option analysis and impact analysis. Option analysis with getting help from innovative methods tries to find a new solutions and methods and its output is the list of options. The impact analysis phase tries to select the best option according to the criteria of risk reduction and cost analysis.Appling the process in Garmdarreh_Level Crossing exhibited that risk could easily demonstrate the safety state of a system and also it showed how modeling and generating causal and consequence charts can help researchers to more easily and more reliable find a solutions and options for reducing risks. The application also shows that the process capability completely covers all the hazards in the scope.