Detailed safety requirements for the design of railway systems emerge from codes standards and guidelines e.g. CENELEC, NFPA, UIC, IEC, EUROCODES.
The hazard log is created from the start of the project and accompanies the project through all stages from concept to operation.Hazards are identified in a systematic way using HAZOP techniques. Frequencies and possible unwanted consequences are classified for each hazard. A matrix screening method ranks the hazards and identifies hazards to be subject for further risk reduction, e.g. in accordance with the ALARP principle. For the most significant hazards, a detailed risk assessment may be carried out.
The main goal is to assess and if necessary to complement planed risk reducing measures in the most cost-effective manner to achieve the chosen level of risk.Detailed probabilistic models may be developed and applied, based on data from past accidents. The probabilistic models may be analytical, e.g. Bayesian networks or Monte Carlo simulations.Assessment of consequences may be carried out using simple analytical tools or elaborate computerised methods like Computational Fluid Dynamics (CFD) or simulation of evacuation scenarios.
Depending on the results of the risk assessment, additional risk mitigating measures may be considered. Cost-benefit analyses may be performed as basis for selection between alternative risk reducing measures.