Looking for ways to improve operational and safety performance? We’ll help you assess – and then reduce or control – the risk of human error across your operations.


Our clients in safety critical industries want their systems to be of the highest technical integrity, and lead the way in operational and safety performance. These goals are extremely challenging and there’s always room for improvement. We still experience too many near misses, incidents and accidents because of people getting things wrong.

We help our clients with their ambitions here. We’ll start by analysing proactively your operations, looking at the types of potential human error and the probability of these happening. You’ll understand what effect such risk will have on system safety. You’ll have ways to control or reduce human error so that it’s as low as reasonably practicable (ALARP).

What we offer

To assess the potential human errors within your system, and possible effects, we use Human Reliability Assessment (HRA).

There tend to be three main stages:

  1. Identifying human error
  2. Screening analysis
  3. Quantifying human error.

To meet regulatory requirements, we may recommend our full human factors safety critical task analysis (HFSCTA).

Stages of Human Reliability Assessment

Stage 1: Identifying human error

This is a critical part of human error analysis. You need to know about all the potential risks, so you don’t underestimate the threat to system safety and performance. This stage can be used to assess human errors qualitatively, and form the basis for quantifying error (stage 3). 

 We’ll use several proven techniques, particularly a human HAZOP (hazard and operability study). This variant of an engineering HAZOP focuses on human error. You’ll have a choice of approaches. Your human HAZOP can form an integral part of your engineering approach by adjusting it accordingly (including guide words for identifying human errors and their underlying causes). Or we can perform it independently. 

 Key steps

  • We break down your operator’s tasks into component actions with a formal analysis. Actions are assigned to the relevant system components to be analysed in the HAZOP.
  • Each system component is assessed in terms of operator actions. For each action involving the component, we identify potential human errors.
  • We identify human errors with an extensive list of external error modes (EEMs). Each EEM is a simple keyword or term (for example, ‘failure to detect signal’, ‘incorrect interpretation’ or ‘selects wrong procedure’). These are categorised by the type of activity.
  • Our analysis uses a similar categorised list of the underlying psychological error mechanisms (PEMs). These are the cognitive explanations of the errors (for example, ‘lapse of attention’, ‘inadequate time perception’ and ‘cognitive overload’).
  • For each PEM, we use a list of possible error reduction mechanisms.
Stage 2: Screening analysis

Here, we identify errors that can effectively be excluded from further analysis, and those which should be assessed further. We do this by assigning a probability of 1.0 to each human error and then examining the consequences. The probability of 1.0 reflects a worst-case scenario, so any negative effects will be exaggerated. Errors found to have a negligible effect aren’t analysed further. Significant errors are then quantified.

Stage 3: Quantifying human error

If we’ve carried out screening analysis, we only need to look at errors found to have a significant system effect. We assess system safety numerically, calculating human error probability in various ways, including the Human Error Assessment and Reduction Technique (HEART). The output allows tasks to be compared relative to each other. We’ll assess each individual task in turn.

  • First, we specify the generic nature of the task.
  • We then identify error producing conditions (EPCs). For example, ‘unfamiliarity’ or ‘low-signal-to noise ratio’.
  • Next, we specify the extent of each EPC effect, assigning a value between 0 and 1.
  • We calculate the final error probability.

What are the benefits?

There are several safety and commercial advantages when predicting, documenting, reducing and controlling human-related risks and errors. 

  • You’ll make a positive impact on incident and accident rates.
  • You’ll make the working environment safer for your personnel and contractors.
  • You’ll justify design decisions and save money on costly re-designs.
  • You’ll understand where new competencies or extra training is required.
  • You’ll improve all-round operational performance. 

Why choose LR?

You’ll get the support of leading human factors and working environment specialists, who know how to use best practice human factors tools and techniques for your industry. 

  • You’ll benefit from our human error analysis experience, including human HAZOP, in a variety of applications.
  • We go beyond approaches used by many human factors practitioners. Our approach is based on a combination of human error identification techniques, as well as an engineering HAZOP.
  • By categorising EEMs and PEMs, we simplify the analysis while covering each of the three levels of human-information processing: skill, rule and knowledge-based.
  • You’ll address the underlying causes of errors at both interface and organisational levels with our robust reduction mechanisms.
  • Our versatile approach can be performed independently or as part of an engineering HAZOP.
  • You’ll have a hybrid HAZOP team on your project. Our human factors expertise is supplemented with the in-depth knowledge of our system specialists.