What are the 5 Safety Studies that can be requested from us in a railway project?


The Safety Case is a structured study supported by a body of evidence that provides a convincing, understandable and valid analysis that a system is safe for a given application in a given environment.

One of the most interesting characteristics of a Safety Study or Safety Case is its "Incrementality": The development of the system moves along a Life Cycle and so does the Safety Management associated with the project and, therefore , to the Life Cycle of the System . The Security Case should not be considered only a summary of the Security activities carried out throughout the Life Cycle , which will be published before the transfer of the system to the customer. Rather, it should be viewed as an integral part of the System Life Cycle and as a supporting document for the achievement of key milestones or milestones.               

 The rail industry has increasingly recognized that Safety Study preparation is not an activity that should be left at the end of the safety life cycle. In fact, Safety standards and local regulatory authorities often require incremental development and submission of the Safety Study at each major Project milestone, until the system is handed over to the operation and maintenance authorities.

Although there are variations in Security Life Cycle requirements between different regulatory domains, the most common Security Studies are as follows:

  • [ SAFETY STUDY 1] Preliminary Safety Case: after completion of the requirements specification phase.
  • [ SAFETY STUDY 2] Design Safety Case : Also called "intermediate safety case", after completion of design and initial validation activities.
  • [ SAFETY STUDY 3] Final Safety Case , also called "Operation Safety Case ", after completion of validation activities and before entering service.

Interestingly, one might question the value of preparing a preliminary Safety Case as the latter is developed before detailed design specifications are available and therefore no detailed safety analysis is yet possible.

However, the advantage of the Preliminary Safety Study is to provide a skeleton for the Safety argument that can be used to manage the evidence that will be collected in later stages, and allow early discussion with regulatory authorities and other stakeholders. It may also list existing limitations and assumptions relevant to situations such as a running railway being upgraded, a very typical application in the railway industry.

In addition to supporting the achievement of certain stages of the project, the Security Study must be prospective, that is, contain enough detail to give confidence that the Security objectives will be achieved in the later stages and identify any restrictions imposed on them.    

In the context of a Life Cycle of development of a traditional railway system, the following Safety Studies may be produced, in addition to the above :

  • [ SAFETY STUDY 4] Commissioning Safety Case: delivered after completion of equipment installation; demonstrates that static and dynamic testing can safely begin.
  • [ SAFETY STUDY 5] Safety Case vacuum tests: produced after completion of dynamic tests; It argues that the trial operation can safely begin. The characteristics and objectives of the five staggered deliveries of the Safety Study are shown in the following:

Preliminary Design - Preliminary Safety Study

  • Make a statement of the project strategy, consideration of design options, and a description of the resulting conceptual design sufficient to allow the identification of major rail safety hazards , control measures, and protection systems.
  • Provide a description of the process that is being carried out to demonstrate compliance with the legal duty regarding risk reduction . Provide an overview of the approach, scope, criteria, and results of Security analysis (random failure analysis and systematic failure).
  • Define the application and environmental conditions in which the system will or should operate.
  • Provide explicit references to standards and design codes used, justifying their applicability and the demonstration that they have been met, will be met or justify, failing that, the exceptions to them.
  • Provide information on quality management for the design, including design controls, standards control, verification and validation, and the interface between Safety design processes .
  • Give a statement with details of the Security Study development process , including the work teams, the independence of the RAMS analysis , and support for an Implemented Security Management System .
  • Provide information on the quality management system for the production of the Safety Study .
  • Identify and explain any new or newly developed characteristics for the company or organization, including their importance for Safety , which increase uncertainty and, therefore, risks.

Final Design - Design Safety Study

  • Explain how decisions regarding the achievement of Safety Functions ensure that risks will be reduced to an acceptable level.
  • Provide sufficient information to support the claims made in the preliminary Safety Study .
  • To demonstrate that detailed design support will meet the Safety Objectives before construction or installation begins and that sufficient analysis and engineering checks have been performed to demonstrate that the installation will be safe.
  • Provide detailed descriptions of the system architectures, their Security Features, and reliability and availability requirements .
  • Confirm and justify the codes and design standards that have been used and where they have been applied, the non-compliances and their justification.
  • Identify the initial application conditions related to Security that must be respected to maintain the desired Security Integrity .
  • Confirm which aspects of the design and its supporting documentation are complete.
  • Confirm which aspects are still under development and identification of pending works that will be addressed.

Installation, testing and commissioning - Commissioning Safety Study

  • Demonstrate that the system, as manufactured and installed, meets the relevant Safety criteria and it is possible to initiate safe static and dynamic tests .
  • Allow the production of a program of commissioning activities that: Will demonstrate as far as possible the safe operation of all systems and equipment; It will demonstrate to the extent possible all Security claims ; Confirm as far as possible all Security assumptions ; It will confirm as far as possible the effectiveness of all procedures related to Security .
  • Demonstrate that commissioning activities can and will be carried out safely and that operational procedures for commissioning are supported by the Safety Study .
  • To demonstrate that no safety aspects remain to be demonstrated after completion of commissioning activities.

Blank Running Tests - Vacuum Testing Safety Study

· Demonstrate that the system (built and commissioned) complies with the safety standards and criteria established in the Safety Study prior to commissioning.

· Demonstrate that analyzes and tests have been carried out to demonstrate that the system will operate Safe .

· Capture any relevant design changes that have occurred during commissioning activities and to analyze and justify their effect on System Security .

· To identify Security- related application conditions that will be adhered to during test operations to maintain the desired Security integrity of the system, including temporary mitigations and restrictions .  

Operation with passengers - Final Safety Study

  • Demonstrate that the system (as tested under similar operating conditions) complies with the Safety standards and criteria established prior to commissioning, and is ready to begin passenger operation.
  • Identify the final application conditions related to Security that will be respected during passenger operation to maintain the desired Security integrity .
  • Demonstrate compliance with legal requirements to reduce risks to workers and the public to an acceptable level.

As we can see, the Safety Study develops gradually or this should be the philosophy that will accompany our railway projects; therefore, it is perfectly normal to submit or close a Security Study before the required evidence is fully available, as long as any missing information or open issues are clearly identified.

In some cases, even the five deliverables explained in this article may not be enough. For example, a Construction Safety Study may need to be divided into two stages: construction and installation.

Similarly, a Commissioning Safety Study may need to be divided into more subsystems related to different technologies, such as power supply, for a to side, and signage on the other.

Typically, the initial version of any Security Study is provided as a starting point to discuss the approach and structure of the Security demonstration with project stakeholders and to provide a Security demonstration and rationale covering the packages. more advanced workstations.   

At Leedeo Engineering , we are specialists in the development of Safety Study and Analysis (Safety Case) according to the CENELEC EN 50126, EN 50129 standard. Do not hesitate to contact us for more information about our services. Contact >>  

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