Safety Layers at Level Crossings

Kurzfassung

In 2005 more than 880 people were killed or seriously injured at level crossings in the EU. Those are almost 30% of all people that were killed or seriously injured in railway accidents in the EU in that year. The numbers show that increasing safety at level crossings is one of the great challenges of these days. To increase safety at level crossings it is necessary to identify the weaknesses of the level crossing system. The system, i. e. the level crossing, is considered to be protected by several safety layers. Every weakness can be seen as a gap in one of these safety layers. The Swiss Cheese Model of James Reason is a good way to illustrate the layers and their existing gaps. Detailed knowledge about the layers can be turned into a model of safety layers called MoSiS. MoSiS is currently being developed at the Institute of Transportation Systems of DLR and is expected to become a useful tool in increasing safety at level crossings. A way to identify gaps and weaknesses in safety layers is accident analysis. There are several methods available for analysing accidents. One of them is the Why-Because Analysis (WBA) of Peter Ladkin. WBA allows a structured causal analysis of the accident including technical equipment, human factors and organisational aspects. The objective of WBA is to find out why an accident happened and how a recurrence can be prevented. Its objective is not to answer the question of guilt but to find all causal factors that contributed to the accident. At the Institute of Transportation Systems of DLR, WBA has been used to analyse several level crossing accidents. One of these analyses shall be presented. WBA identifies certain root causes that indicate gaps in the safety layers. The knowledge about these gaps will contribute to the model of safety layers called MoSiS. MoSiS will show the gaps in the safety concept of a system (i. e. the level crossing) and help closing these gaps efficiently. Closing a gap means deleting a root cause of an accident, thus preventing the accident from happening again. MoSiS will include all root causes from all level crossing accidents that have been analysed. It will point out various gaps in the level crossing’s safety concept and thereby will help increasing the safety at level crossings. The concept of MoSiS is not restricted to level crossings. It can be extended to become a model of safety layers of the whole railway system.