A hazard-related use scenario is a use scenario in which one or more user actions, in combination with context of use, user characteristics or system properties, can contribute to a hazardous situation or to harm. It describes not only a user action but the complete chain of events consisting of tasks, possible use errors, contributing context factors, hazard, hazardous situation and possible harm. According to IEC 62366-1, they are derived from the identified hazards and hazardous situations and form a central link between usability engineering and risk management according to ISO 14971.
Role in the usability engineering process
Hazard-related use scenarios typically arise from linking the use specification, task analysis and risk management. They describe not merely user tasks but focus on use workflows in which a use error or another use-related factor can lead to a hazardous situation. According to IEC 62366-1, they are derived from the known or foreseeable hazards and hazardous situations. In accordance with IEC 62366-1, the description of a hazard-related use scenario must include all relevant tasks and their sequence as well as the severity of the possible harm associated with it. They form the basis for selecting the scenarios that are tested in the summative evaluation and for deriving risk-reducing measures.
Delimitation from use scenario and user task
An ordinary use scenario describes a use workflow irrespective of its safety relevance. A hazard-related use scenario, by contrast, explicitly establishes a link to a hazard or hazardous situation. A user task describes only a single user action or work step, whereas a hazard-related use scenario typically comprises several related user tasks including context conditions.
| Term | Describes |
|---|---|
| Use scenario | A use workflow irrespective of its safety relevance |
| Hazard-related use scenario | Explicitly establishes a link to a hazard or hazardous situation. Typically comprises several related user tasks including context conditions |
| User task | Only a single user action or work step |
Relationship with critical tasks
FDA documents focus primarily on critical tasks, that is, user actions whose erroneous performance can lead directly or indirectly to harm. There is a close relationship between the two concepts: A hazard-related use scenario often comprises several tasks, some of which are classified as critical tasks. While IEC 62366-1 works more scenario-based, FDA documentation concentrates more on the safety-critical tasks within these scenarios.
Derivation and description
They are usually created by combining the following information: use specification, context-of-use analysis, task analysis or hierarchical task analysis (HTA), use error analysis and risk management according to ISO 14971. A complete hazard-related use scenario typically describes the user group, context of use, goal of the action, relevant user interactions, possible use errors and the resulting hazardous situation. This creates a comprehensible link between risk analysis and usability evidence.
Significance for formative and summative evaluations
Hazard-related use scenarios largely determine the scope of safety-relevant usability tests. In formative studies, they are used to examine risk-bearing interactions early and to uncover design flaws. In summative evaluations, they form the basis for selecting the safety-critical test tasks and use scenarios. An incomplete set of hazard-related use scenarios can lead to relevant risks not being examined in validation.
Typical weaknesses in practice
A frequent problem is reducing hazard-related use scenarios to individual operating errors. This loses important context factors, for example time pressure, environmental conditions or user qualification. Mixing up hazard, hazardous situation and user task is also widespread. This makes traceability between the risk management file, usability engineering file and evaluation reports more difficult.
Regulatory reference
IEC 62366-1 requires the identification and documentation of hazard-related use scenarios as part of the usability engineering process; they serve as the basis for deriving use-related risks and for planning evaluations. ISO 14971 establishes the practical link between user interaction and risk management. Use-related hazards and use errors must be included in the risk analysis. In its human factors guidance, the FDA mainly uses the term critical task but also refers to hazard-related use scenarios in the context of safety-relevant use situations; for human factors validation testing, the use scenarios used are to be described and the critical and non-critical tasks contained in them listed. The MDR and the IVDR also require in Annex I that foreseeable misuse and ergonomic features be taken into account; hazard-related use scenarios provide the concrete basis of evidence for this.
A hazard-related use scenario links use scenario, critical task and hazardous situation into a comprehensible chain of events. It largely determines which tasks and interactions must be examined in formative and summative evaluations.
Frequently asked questions (FAQ)
Is every use scenario automatically a hazard-related use scenario?
No. A normal use scenario merely describes a use process. Only when there is a link to a hazard or hazardous situation is it a hazard-related use scenario.
Is a hazard-related use scenario the same as a critical task?
No. A hazard-related use scenario describes a complete safety-relevant context of use. A critical task is a single safety-critical user action within such a scenario.
Do hazard-related use scenarios have to be tested in summative studies?
IEC 62366-1 first requires the identification of all known or foreseeable hazard-related use scenarios. Subsequently, on the basis of a documented selection procedure, those scenarios are selected that are included in the summative evaluation.
Are hazard-related use scenarios taken over directly from the risk management file?
Not completely. They typically arise from the combination of risk analysis, task analysis and context-of-use analysis. The risk management file provides the safety-relevant starting points.
Do you want to identify hazard-related use scenarios for your medical device and embed them in your risk analysis? We support you throughout the usability engineering process according to IEC 62366-1.
More about our usability engineeringSources
- IEC 62366-1:2015+AMD1:2020, Medical devices, Part 1: Application of usability engineering to medical devices
- ISO 14971:2019, Medical devices, Application of risk management to medical devices
- Regulation (EU) 2017/745 on medical devices (MDR)
- Regulation (EU) 2017/746 on in vitro diagnostic medical devices (IVDR)