Keeping the balance between overload and underload during partly automated driving: relevant secondary tasks

Zusammenfassung

In partly automated driving the driver has to both monitor the system and be able to take over driving immediately if necessary (SAE Level 2: L2) [SAE16]. The optimal monitoring performance is reached if the driver is neither under- nor overloaded in terms of strain [DeW96]. Advanced driver assistance systems may assist the driver in remaining in this optimal load during potentially long, monotonous automated drives. This is evaluated in a driver simulator study. The study assessed the impact of several secondary tasks (ST), naturalistic as well as standardized, during partly automated driving. 34 participants went through eight test conditions: Two baseline drives (manual driving (L0) and L2 without secondary activity) and six conditions with a L2 automation and different secondary activities. These activities included an auditory n-back task (1- and 2-back) (e.g. [Lor15]) and the surrogate reference task (SuRT) [ISO14198]. Furthermore, an activating task (stretching exercises) as well as a condition in which a video was played were integrated. Subjective strain was measured by using questionnaires (Subjective Experienced Stress: SEA; Stanford Sleepiness Scale: SSS), objective strain in terms of monitoring performance by using a detection task. The results suggest that visual secondary tasks lead to a decrease in drivers’ monitoring performance – not necessarily reflecting the drivers’ perceived strain. For example, subjectively demanding auditory tasks did not lead to substantial monitoring lapses but may induce positive effects in potentially monotonous automated driving situations.