Analysing and Modelling Risk

The rail industry's learning process began in its earliest days, the first Railway Regulation Act establishing both a Railway Inspectorate and a requirement to report all injurious accidents to the Board of Trade.

Risk analysis

That was in 1840. Within 50 years, block signalling, interlocking and continuous braking on passenger trains had been made mandatory; the next century would see many more improvements, ranging from continuous welded rail to automatic train protection systems – new technologies which often came out of investigations.

How we support industry

The cycle of performance reporting has become essential to ensuring that this development continues. But while statistics show the railway has got steadily safer over time, we know that good performance can breed complacency. It also makes it harder to spot trends and identify emerging issues, as there are fewer events to plot on charts.

To combat both these problems, RSSB tracks accident precursors – like signals passed at danger – and analyses risk (risk being a combination of the number of times something happens and its likely consequences).

Together, RSSB's consideration of safety performance and risk helps the rail industry make informed judgements and take safe decisions.

RSSB has produced a number of accident investigation resources. We provide analysis of safety data that is collected through a range of reporting systems, as well as learning from accident investigations.

Safety Risk Model

A good understanding of risk is required to deliver a safer, more efficient and sustainable rail system. RSSB’s Safety Risk Model provides a network-wide view of risk and is used by companies and projects to support risk-based decision making.

What is the SRM?

The Safety Risk Model (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.

  • It provides a trusted starting point for quantified risk analysis. For example, it was instrumental to the development of new rules for train radio failures and defective on-train equipment, and supported train operator decisions about retro-fitment of train doors and TPWS equipment.
  • Train operators use the SRM-Risk Profiling Tool to understand the safety of their operation. This forms part of their suitable and sufficient risk assessment, which is required by ROGS.
  • The SRM national risk profile helps to focus collaborative cross-industry effort and informs the industry strategy Leading Health and Safety on Britain’s Railway.
  • SRM risk estimates are used to calibrate other industry risk tools, including the tools Network Rail uses to manage risk from with signal over-runs and at level crossings.

How does the SRM measure risk?

The SRM estimates the underlying risk from the operation and maintenance of the mainline railway.

It comprises a series of models representing the hazardous events with potential to cause harm to workforce, passengers and other members of the public. RSSB uses the model to produce risk estimates for 131 hazardous events and almost 3,000 event precursors.

The SRM 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. To calculate FWI injuries are weighted according to their relative severity.

Risk estimates are derived from historical accident data, fault and event-tree modelling, structured expert judgement from technical specialists, and statistical methods.

How can I use the SRM?

A brief overview of SRM version 8.5 is available to download below.  RSSB members and affiliate members can also access full tables of risk estimates below.

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.

Contact for the SRM

For more information and guidance on the SRM, contact Chris Harrison our Principal Risk Analyst.

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