“…An affective in-car system must, first of all, be aware of the driver's state [22], which is comprised, e.g., of physical features, mental workload, fatigue, the level of distraction, and emotions [16,23]. Psychophysiological measures like heart rate variability, skin conductance, skin temperature, breathing rate, or EEG can be used to deduce driver states [24][25][26][27][28]. At the same time, unobtrusive contactless technologies like audio-visual sensors or eye-tracking might have lower initial hurdles regarding acceptance in cars: a video stream of the driver can be used to extract facial action coding units, which in combination with voice features can inform an emotion detection system [29,30], and measures of pupil diameter can be used to assess mental workload [31].…”