A practical guide for health and safety leaders
How to measure workload at work
When people talk about workload at work, they often mean different things. Sometimes they mean the job is physically demanding. Sometimes they mean it is mentally tiring. Sometimes they mean people are under time pressure, making more mistakes, or finishing the shift drained. HSE explains that workload matters because people have limited capacity for processing information, holding items in memory, making decisions, and performing tasks. HSG48 also makes clear that both excessive demand and poorly designed work systems can increase the likelihood of human error.
For health and safety leaders, the problem is that workload is often judged informally. A task may look manageable on paper but feel very different in real use. HSE’s human factors guidance is useful here because it frames performance around the job, the individual, and the organisation, rather than treating workload as an isolated issue. That makes workload assessment far more practical for real world risk management.
Start by understanding the task
Before measuring workload, it helps to understand the job properly. HSE’s guidance on human factors in risk assessment says organisations need an adequate understanding of the human role in the task or activity, especially where work is safety critical or exposes people to health hazards. In practice, that is why a structured task analysis, such as HTA, works well as a starting point. It helps break a task into goals, steps, decisions, and plans so you can see where demand is likely to rise.
This matters because workload rarely sits evenly across a whole task. HSE’s workload guidance recommends carrying out a task analysis to understand exactly what staff are required to do, when they need to do it, and what information they need. It also says task analysis should consider both physical and mental workload, including visual inputs, auditory inputs, cognitive activities, and psychomotor skills. If you do not first understand the task, you risk measuring workload in a vague way and missing the real pressure points.
NASA TLX is often the best practical starting point
Once the task is understood, one of the most practical tools to use is NASA TLX. Although it is not a UK method, it remains one of the best known workload assessment tools and is often a sensible starting point for structured discussion. NASA describes it as a subjective workload tool based on six dimensions: mental demand, physical demand, temporal demand, performance, effort, and frustration.
For a health and safety audience, the value of NASA TLX is straightforward. It helps show whether a task feels demanding because it is mentally complex, physically tiring, rushed, frustrating, or hard to perform well. Used after HTA, it becomes easier to link high ratings back to particular parts of the task, particular decisions, or particular operational constraints. HSE’s workload guidance remains important around it because it emphasises the need to assess workload during normal work, unusual activities, peaks, and emergency situations, and to consider issues such as staffing, competence, role clarity, and shift patterns as part of the overall picture.
Where the Bedford Workload Scale fits
Not every organisation needs a detailed diagnostic profile every time. Sometimes the key question is simpler: was the workload acceptable, or was it too high? That is where the Bedford Workload Scale can be useful. NASA’s cognitive workload technical brief describes Bedford as a simpler one dimensional judgement about spare mental capacity, while noting that NASA TLX can provide more diagnostic detail about the type of demand being experienced.
From a practical point of view, that means NASA TLX is often more useful when you are trying to understand why a task is demanding, while Bedford can be useful when you want a more direct judgement on whether enough mental capacity remained. HSG48 supports that wider human factors principle by stressing that demands should be matched to human capabilities if reliable performance is the goal.
Other workload methods worth knowing about
Two other methods are worth brief mention. Instantaneous Self Assessment, or ISA, was designed to capture workload ratings during task performance. The original evaluation found that ISA ratings correlated with post task workload ratings, heart rate variability, and task performance, but the act of giving ISA responses also made primary task performance worse during those response periods. In other words, it can be useful when workload changes across a task, but it can also interfere with the work.
The Workload Profile is another multidimensional method. It can give more diagnostic information about the nature of task demands, especially where different kinds of mental processing are competing. For most health and safety teams, however, these are methods to know about rather than methods to start with.
Do not rely on self report alone
This is the most important practical point. Subjective tools are valuable, but they are strongest when they are combined with other evidence. HSE’s workload guidance and HSE’s human factors guidance both point to the need to understand the wider work system, not just a worker’s opinion in isolation. That means looking at what is happening operationally as well: delays, variability, quality issues, rework, near misses, or signs that the task is pushing the system too hard.
The same point comes through in the wider workload literature. A systematic review of physiological measures of mental workload found that no single physiological measure was valid in all task scenarios. The best picture usually comes from combining subjective, performance, and sometimes physiological measures rather than relying on one method alone.
Where fatigue fits
Fatigue is related to workload, but it is not the same thing. HSE’s fatigue guidance describes fatigue as a decline in mental or physical performance resulting from prolonged exertion, sleep loss, or disruption of the internal clock. HSE also notes that workers are more easily fatigued if their work is machine paced, complex, or monotonous. That is a useful distinction for industry. Workload methods help you understand the demands of the task. Fatigue management helps you understand the wider risk created by working time, shift design, recovery, and sustained alertness.
That is why fatigue monitoring technology, where used, should be seen as an additional layer rather than a replacement for task analysis or workload assessment. HSE’s fatigue guidance is clear that fatigue needs to be managed like any other hazard, and that compliance with working time rules alone is not enough to manage fatigue risk.
A practical recommendation for health and safety leaders
For most workplace studies, the strongest starting point is straightforward. First, understand the task using HTA or another structured task analysis method. Second, use a practical workload tool such as NASA TLX to understand how demanding the task feels. Third, review performance and operational data to see whether the demand is affecting safety, quality, productivity, or reliability. Fourth, consider fatigue risk separately, especially where shift work, long hours, or sustained alertness are genuine concerns.
Used properly, workload assessment is not just a questionnaire exercise. It is a practical way of making better decisions about task design, staffing, process change, and risk control. That is consistent with HSE’s human factors approach, which focuses on designing work and systems that are fit for people and capable of supporting safe, reliable performance.
About the author
Stephen Bowden is a Chartered Ergonomist and Human Factors Specialist at Morgan Maxwell. He has around 18 years of experience helping organisations improve the design of work, reduce musculoskeletal risk, and understand how real tasks affect safety, performance, and productivity. His work spans manufacturing, office environments, and safety critical systems, with experience supporting organisations including Rolls Royce, Specsavers, the NHS, VELUX, and other complex operational businesses.
Stephen holds a BSc in Ergonomics and Human Factors from Loughborough University and is a Chartered Member of the Chartered Institute of Ergonomics and Human Factors. His work focuses on practical, evidence based ergonomics, including task analysis, workload assessment, workplace design, manual handling risk reduction, and digital human modelling.
