Assessing the risk to railway structures from train impact

Designers of railway structures frequently find that they have difficulty meeting the requirements for design of structures to resist impact loads from a derailed train. Potentially such loads can be extremely high, especially where a very substantial proportion of the train mass can be mobilised at line speed, as was the case for the Eschede incident in Germany. It is rarely economical to design structures for such extreme loads and design standards such as BS EN 1991-1-7 set impact load values that are intended to provide a minimum level of robustness for safety and economy. However, the safety benefits compared to the cost of providing sufficient resistance, even for the loads in design standards, can be difficult to justify in some cases. Risk assessment can be used in such circumstances to demonstrate achievement of an acceptable level of safety at reasonable cost. Application of the risk assessment methodology in UIC leaflet UIC-777-2R is described, highlighting the availability of Rail Safety and Standards Board (RSSB) derailment risk data and RSSB guidance on taking safe decisions.