Automation triggers usually refer to the those used in machine-triggered automation. Triggers are designed primarily to invoke types or levels of automation which are suited for the current workload of the operator. The aim is to keep the operator’s workload within a band of workload, not too high or not too low.
Automation triggers include:
Performance: The performance of the operator is measured in real-time. If the performance drops past a pre-set criteria, automation can be activated.
Physiological: Various physiological measures may indicate a high mental workload, and automation can be invoked. These measure include heart rate, skin conductivity, and eye movement/dilation.
Modelling taskload: By measuring performance at various task loads for a specific set of tasks, we may find the taskload where the operator needs assistance, and subsequently design the automation to invoke when this taskload is reached.
Critical events: There may be times during a operator’s shift, when an event may occur where automation may be altered, turned on, or turned off.
Hybrid: A combination of two or more trigger types may be the most effective in matching the operator’s workload.
Each of these trigger types has drawbacks. A performance trigger is reactive, and that which is to be avoided (poor performance) has already occurred before automation is triggered. Although physiological triggers can indicate high workload when no other signs are apparent, they are also reactive and don’t account for the indirect relationship between physiological indicators and performance. An operator may be making an extra effort and have higher stress levels, but still performing well. For modelling, a database of taskload and performance measures must first be constructed, then a decision made for a trigger point. Critical events are usually quite specific for the tasks, and subsequent triggers difficult to generalise. Combining triggers are currently seen as promising however their aforementioned disadvantages are only mitigated by their combination.
One other consideration is who has the authority to vary the automation in real time? The designer (the machine) or the operator?