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Safety Risk Model

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Safety Risk Model

Chris Harrison

Principal Risk Analyst

Our members need to have a good understanding of risk to deliver a safer, more efficient and sustainable rail system. The Safety Risk Model provides a network-wide view of risk and is used by our members to support risk-based decision making.

​What is the Safety Risk Model?

The Safety Risk Model - also known as the SRM - provides a network-wide risk profile for the GB railway. It has underpinned the industry’s evidence and risk-based approach to safety management for the best part of two decades.

Our risk specialists use structured expert judgement combined with historical accident data, fault and event-tree modelling, and statistical methods to derive risk estimates which can then be used to inform decision-making by industry.

RSSB members benefit from both access to the SRM itself and to our team of world-class technical experts who can help members get the most out of the model.

The SRM saves members money as they don’t need to invest in their own individual models or buy in risk analysis support from elsewhere.

How does the SRM work?

The SRM is actually made up of a series of smaller models, representing the hazardous events with potential to cause harm to workforce, passengers and other members of the public. From this we can produce risk estimates for 131 hazardous events and almost 3,000 event precursors.

The model measures risk in terms of frequency, how often we expect something to occur, and consequence, the expected level of harm that arises when it does. Risk is presented in units of Fatalities and Weighted Injuries (FWI) per year.

This is a way of measuring the level of harm or risk in a consistent way, by combining the fatalities, major injuries and minor injuries in one unit of measurement.

Each injury type is weighted relative to one fatality according to their severity.

By providing a trusted starting point for quantifying and understanding the risk, it is possible for companies to target investment and intervention to ensure it is managed and mitigated appropriately, and in a way that offers value for money.

Benefits

You can use SRM to support risk assessments and to understand how the risk from your operation compares with and contributes to the network-wide risk. This can help you take and justify safety-related decisions with confidence in line with the rail industry’s Taking Safe Decisions framework.

The SRM has been instrumental in:

  • Fulfilling train operators’ regulatory requirements in ROGS by forming part of suitable and sufficient risk assessments
  • The development of new rules for train radio failures and defective on-train equipment, and supporting train operator decisions about retro-fitting train doors and TPWS equipment
  • Focussing collaborative cross-industry effort and informing industry’s safety strategy Leading Health and Safety on Britain’s Railways
  • Calibrating other industry risk tools, including the tools Network Rail uses to manage risk from signal over-runs and at level crossings

The latest update to the SRM

The overall risk estimated is 139.4 FWI per year, excluding the direct risk from suicides. This risk can be broken down in different ways, with the table below showing high level accident types.

Safety Risk Model table

Among the main changes from the previous update (version 8), which was completed in 2014, are:

  • Reduced risk from collisions between trains and road vehicles at level crossings, which have been subject to numerous safety improvement initiatives and a programme of crossing closures.
  • Reduced risk from passenger train derailments, which is due to a lower estimated frequency from different causes and is likely to reflect improved asset integrity and asset management.
  • A large increase in the estimated frequency of assaults on passengers and public and a smaller increase in the underlying risk. This is at least partly due to improvements in British Transport Police crime recording, which has had the greatest impact on less serious crime categories.
  • An increase in the estimated risk associated with workforce road vehicle driving. There has been sharp industry focus on this risk area and the modelled increase is likely to be the result of better reporting to provide a more complete picture of risk.

The update involved:

  • Refreshing the data used to quantify the models to include all recorded events up to 28 February 2017 (prior to the new Safety Management Intelligence System going live).
  • Refreshing all the exposure data used in the models, such as train kilometres, passenger journeys and level crossing usage.
  • A full update to frequency estimates for all the Level Crossing models.

RSSB members can access more information about SRM version 8.5 from the Rail Risk Portal.

Future plans

We will publish a short technical report on the version 8.5 update in May 2018 and analysis and presentation of risk information will be included in the 2017/18 Annual Safety Performance Report, which will be published in July 2018.

We will release an updated Risk Profile Tool incorporating new risk values in autumn 2018.

SRM version 8.5 is an interim update to keep SRM figures current while we redevelop the model to better meet user requirements and align it with SMIS. The first stage of this work is already underway.

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