# HMD-Based VR Tool for Traffic Psychological Examination: Conceptualization and Design Proposition
## 1 Introduction
### VR-Based Simulation Validity  
The general question regarding VR simulations is whether behavioral, cognitive, emotional and psychophysiological responses in VR are equivalent to those happening in real world situations [36]. In the last two decades, studies have demonstrated the validity of driving simulators for driving behavior [37] and the ability of virtual environments to elicit adequate emotional responses [38]. At the physiological level, interactive 3D iVEs have been found to evoke responses that are more similar to responses in real conditions than iVEs with low interactivity [39], which emphasizes the importance of interactive features and the specific haptic interface type. On the other hand, in goal-oriented cognitive navigational tasks people tend to be less time-efficient in virtual simulations [40], which questions the VR tools' reliability for behavioral measures. This notion was also identified in other studies, where the virtual environment promoted worse performance than the physical environment [19]. Based on available research, this fact can be attributed to the limits of the used technology (e.g., image quality, field of view or photorealism), but, above all, to a form of movement metaphor (i.e., UI control), which may not always be easy or intuitive for the user [41]. The virtual simulation should thus always be complemented by the corresponding haptic interface (as discussed below). From a psychological point of view, lower realism in VR usually decreases the realism of mental reactions [39]. The need for a photorealistic level of quality will be soon resolved by the ever-increasing quality of iVR technologies, where better tools are expected to lead to ever-increasing physical and cognitive fidelity and to deeper levels of immersion. Regarding recent advances in VR technologies, the increasing level of immersion corresponds positively to the subjective feeling of presence [42], so the particular type of virtual technology device can affect the level of psychological response. Regarding this, it is generally assumed that the cognitive and behavioral processes demonstrated in immersive virtual simulations as opposed to other forms of simulations (e.g., desktop applications) correspond more truly to the real behavior of an individual in the actual environment [43]. However, summarizing evidence on this issue is still absent and discussion on this topic persists. Generally, VR technologies provide unique potential for the study of natural phenomena through simulations where people can be observed in natural-like conditions [44] since VR technologies support the activation of cognitive mechanisms like those that occur in the real world [45] and may be therefore considered full-fledged substitutes for real-world scenarios [46], including driving behavior. Another strong advantage of VR technologies is the possibility of data triangulation- the possibility to easily combine it with additional measures such as sensorimotor activity or psycho-physiological indicators. In the sense of mixed research design, we speak about concurrent triangulation [47]. Possibility to combine various measuring instruments (complementary measures) represents a viable trend that can benefit from virtual technologies [48]. Since the VR interface can be held indoors, within a controlled environment, the interface can be complemented with different types of measures such as electroencephalogram (EEG) [49]; functional near-infrared spectroscopy (fNIRs); electrocardiogram (ECG); electromyogram (EMG); mechanomyogram (MMG); galvanic skin response (GSR), blood pressure measures (pulse transit time; PTT); photoplethysmogram (PPG); and others. Especially valuable indicators are provided by the human eye movement activity. This non-invasive technique using corneal reflections can be recorded by eye-trackers, which have lately become an embedded part of HMD technology such as with the HTC VIVE pro eye. The eye movements recording, and analysis represent an important factor for understanding the car driving processes [50].