Human factors: Workload
Why is workload important?
Humans have limited capability for processing information (such as from displays, alarms, documentation and communications), holding items in memory, making decisions and performing tasks. Excess workload can result in human performance issues such as slower task performance and errors such as slips, lapses or mistakes. It should also be noted that underload can also lead to human performance issues such as boredom, loss of situation awareness and reduced alertness. Workload issues may be more relevant in times of downsizing or temporarily during peaks (such as incidents or turnarounds).
Workload is related to competence (e.g. some tasks can require less processing in experienced personnel), working hours/patterns (e.g. underload in nightshift control room operators), organisational change (where tasks or roles are changed) and staffing levels. Workload may be higher in some industries/roles where there is an inadequate supply of skilled staff. A high (or perceived high) workload not only adversely affects safety, but also negatively affects job satisfaction and, as a result, contributes to high turnover and staff shortages.
An assessment of workload may be required if you wish to determine whether you have sufficient staff; if capacity exists for additional tasks, or whether personnel can cope with emergencies, incidents or process upsets.
Workload should be assessed if new tasks, equipment, or systems are introduced; or where changes are made to roles and responsibilities.
Key principles in workload
- Performance can be affected by workload being too high - or too low.
- Workload can ‘drift’ over time as new activities are added gradually.
- Ensure that workload has been assessed for emergency situations as well as for normal operating ("steady state") conditions.
- Consider the whole team, and whether tasks can be redistributed between team members or shifts.
- Assess the balance of workload across a shift - can the timing of activities be redistributed to spread workload (e.g. issuing Permits to Work at several periods rather than just at the start of the shift)?
- Workload should be reconsidered during unusual activities, such as ‘campaign maintenance’, or start-up activities on process plants.
- Experienced operators may be able to utilise strategies for handling high task demands; whereas inexperienced staff may be less able to cope (think about when you were learning to drive).
- Perform a task analysis to understand exactly what staff are required to do, when, and what information they need to perform these tasks. Involve the workforce in these analyses.
- Task analysis should consider both physical and mental workload.
- Ensure that workload assessment considers visual inputs (e.g. scanning display screens, looking out of windscreens, CCTV), auditory inputs (telephones, radios, alarms), cognitive activities (analysis of inputs, decision making) and psychomotor skills (physical actions, such as controlling a process using a mouse, keyboard, or buttons and levers).
- Consider not just the number of personnel, but how they are being utilised.
- Set clear roles and responsibilities, ensuing that staff are clear on their priorities. This will help to ensure that even when workload is high, staff are able to focus on key activities.
- Some tasks may be re-allocated from humans to machines/computers, or vice-versa; considering human performance, safety, maintainability, personnel requirements etc.