HP Glossary

HPOG has adopted the following definitions:


It's what individuals do as part of their daily activities and how they carry out individual and group tasks. It's a synonym of behaviour. Identification and management of Human Performance is critical to ensuring robust operations.


Human Factors is the range of physical, psychological, social or organisational influences which affect Human Performance and how people carry out their activities. It is also a discipline concerned with designing equipment, work environments and activities so that people find tasks easy to perform, safe and matched to their strengths and limitations. It is an approach which is integrated into risk management, engineering,  procedure writing, job planning and training.

These are also referred to as Performance Shaping Factors or Performance Influencing Factors,  Error Traps or Error Producing Conditions.


Performance Shaping Factors (PSFs) are a range of conditions that will influence Human Performance including aspects of human factors, worksite conditions, task design and organisational circumstance.  

These can be LATENT or long-term conditions that eventually contribute to an incident. For example, poorly written procedures is a PSF that can lead to misinterpretation, manual handling / no automated alternative is a PSF that can lead to fatigue, unclear roles and responsibilities is a PSF that can lead improvisation etc.

Likewise there may be additional ACTIVE or short-term conditions that affect performance on the day of the incident. For example, poor shift planning / unreasonable deadlines is a PSF that can lead to taking short cuts or stress, restrictive PPE and a hot working environment are PSFs that can lead to dehydration and loss of concentration etc.


In simple terms, WAI refers to how people think the work should be done whilst WAD is what people actually do to get the work done.

Work-as-imagined : Work-as-imagined is what engineers, planners, advisers, managers or anyone else involved in design believe the work should be done, under ideal circumstances. It’s the work-as-imagined picture that determines how a process is set up, how people are trained and which controls need to be put in place.

Work-as-imagined is an idealistic view of the formal task that doesn’t consider how task performance is adjusted to match the constantly changing conditions of work and of the world. Work-as-imagined describes what should happen under normal working conditions.

Work-as-done : Work-as-done is what people actually do to get the job done, taking into account the realities of the situation such as the equipment configuration, and ease of use of the procedure, and the time and resources they have.

Those who have to do the work may find they want to adjust the plans set out in the work-as-imagined in order to get their work done. If this happens without appropriate support, shortcuts may be taken or other habits adopted that can lead to errors.

However, if the difference between work-as-imagined and work-as-done is properly acknowledged and supported, then work can be adjusted safely and lead to reduced risk, increased reliability, and increased engagement.


A statement, usually in probabilistic terms, of likelihood with which a task may be performed successfully by a human being. 

Human Reliability Assessment is the modelling and estimation of the likelihood of human performance being successful, principally in relation to the operation of industrial systems.