What is it?

Human Reliability Analysis (HRA), also known as Human Reliability Assessment, is one of the tools used by Human Factors practitioners, particularly in high hazard and high consequence sectors. The goal of HRA is to identify, assess and substantiate human-related risks based on a proportionate, systematic and evidence-driven process.

HRA is primarily a qualitative endeavour but can utilise quantification methods to support benchmarking, optioneering, risk assessment and risk modelling. The range and depth of these analyses depends on the hazards posed by the the systems and processes being considered and their design maturity.

Why is it important?

Demonstrating that tasks can be performed safely, reliably and efficiently is important wherever people are involved with achieving a goal. Particularly in safety-critical systems, humans are often required to provide defence in depth to fault or hazard progression alongside other safety measures (e.g. passive or automated). It is therefore imperative that:


  • All risk-significant claims placed on the human are identified.
  • The expectations placed on people are feasible and within the capabilities of the human.
  • The design and organisation of tasks support human performance and reliability.
  • Performance shaping factors are identified and assessed.
  • Human-related risks are identified and mitigated or removed.

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HRA can be used to systematically identify where claims are being made on human interactions (explicit or implicit), provide a structure for investigating how these interactions are supported by the system design and training, identify the potential for errors and if necessary, allow a human error probability to be estimated. HRA can provide a vital input into a range of safety management activities, including Safety Cases, Security Cases, Optioneering Studies, and ALARP assessment. HRA also provides the numeric inputs when a Probabilistic Safety Assessment (PSA or PRA in the USA) is being developed or maintained.

What do we do?

We provide a number of services in HRA which include:

Full development and delivery of an HRA programme, including substantiation of Human Based Safety Claims (HBSC), for example in support of a new build project or the UK GDA process.

Provision of bespoke HRA training courses to Engineers and other Human Factors practitioners.

Undertaking specific task analysis and HEP calculations using a variety of techniques to support our clients’ overall programmes.

Integrating our HRA services into an existing safety case or assurance team.

Developing analysis tools and techniques to meet specific needs, for example CRA developed the NARA toolset for EDF.

Conducting or supporting research in HRA, for example on computer-based control rooms or other digital platforms.

Providing Independent Technical Authority (ITA) or Intelligent Customer support to client organisations, using SQEP (Suitably Qualified and Experienced Person) HRA experts from our Human Factors team.

Added value from CRA

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Our experienced team of human factors professionals offers many years of experience in HRA and will assess our clients’ needs to propose a suitable solution. This will depend on a number of variables including the Country and Regulatory environment, design or operating status, immediate challenges requiring resolution and budget available. We would be delighted to explain in more detail how we can support you.

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