Jonas Gruber

Jonas Gruber

Master's Thesis

Influence of Different Stimulus Intensities of Cold Air on Driver Drowsiness


Katharina Jäger (M.Sc.), Madeleine Flaucher (M.Sc.), Dr.-Ing. Heike Leutheuser, Prof. Dr. Björn Eskofier

10 / 2022 – 04 / 2023


Drowsiness while driving is a dangerous state that has an impact on road safety [1]. Compared to driving without drowsiness, it can increase the risk of traffic accidents [2]. In addition to human casualties, there is also a big economic damage [3].

Driving assistance systems can help to reduce the number of accidents. These systems consist of two components [4]: First, the driver’s drowsiness is detected, which is possible through different detection systems such as eye tracking or head tilt observation [5]. The second component consists of suitable in-car countermeasures. [4].

The ways to influence drowsiness can be divided into long-term measures (e.g. improving sleep quality through meditation [6]) and short-term measures (e.g. sleep [7] or caffeine consumption [8]). In the car itself, mainly short term measures come into consideration, such as listening to music [8], the emission of blue light stimuli [9] as well as temperature reduction through car ventilation [10]. However, both the acoustic and visual stimuli have the disadvantage that in certain situations they can distract the driver [11].

This disadvantage is not known for thermal stimuli so far. Studies have shown that driver drowsiness can be reduced by lowering the car interior temperature [12]. Cooling the upper body and especially the facial area leads to activation of the sympathetic nervous system (SNS) of the human body [10, 13, 14]. Activation of the SNS, in turn, increases alertness [10], thereby decreasing drowsiness [15]. However, this effect is only of short duration [16], and some studies suggest that if the stimulus application is repeated, drivers become accustomed to it and the awakening effect thereby decreases or even disappears [17, 18].

Therefore, the aim of this study is to analyse the influence of cold air applied by the car ventilation system on drowsiness during driving. Further, the effect of a more intense stimulus on its repeatability as well as the habituation of the subjects to the stimulus is investigated.

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