## 3 Materials and Methods
### Development of VR Tests for Pedestrians: Procedure and Questionnaires  
The tests that make up the experimental VR session are held with a sample of 29 users with similar socio-demographic conditions (age: 20-30 years; gender: 28% female, 72% male). All of them are Spanish undergraduate, master's, and doctoral students at the Universidad Politecnica de Madrid (UPM). The gender distribution (Figure 3) is representative of the overall sample of UPM students in undergraduate and postgraduate courses [32]. Figure 3: Gender distribution of the sample of users that performed the experimental VR session (by age group). Before starting the tests, each subject fills in a disclaimer with their personal information and history of road traffic accidents, as well as the Simulator Sickness Questionnaire (SSQ), which will be repeated throughout the individual session to identify possible physical affectations in the subject due to VR use. Before the potential collision tests, the System Usability Scale (SUS) questionnaire on the usability of the application is also carried out. Finally, they are also asked to complete the Presence Questionnaire (PQ) for evaluating the interaction with the 3D environment. Simulator sickness results in a sense of nausea, dizziness, vertigo, and sweating (among other symptoms). To this end, the Simulator Sickness Questionnaire (SSQ) has been used as reported in [6]. In it, the users are asked to rate sixteen possible symptoms on a four-point Likert scale (Table 2). This evaluation allows scoring in the discomfort categories falling including the nausea, oculomotor, and disorientation categories, plus a general score by combining the previous ones. The SUS [33] is a ten-item questionnaire with a five-response Likert scale (Table 3). The Likert formatting ranged from \"strongly disagree\" to \"strongly agree\", scaling all values from zero to four, with four being the most positive response (Figure 4). Finally, after summing all individual scores, this result is multiplied by 2.5 to obtain the overall value of SUS. This will convert the range of possible values from zero to one hundred. The researchers [35] investigated the structure of Version 2.0 of the Presence Questionnaire (32 items) by conducting a cluster analysis of PQ data. Only those PQ items that contributed to the reliability of the scale (19 items) were included in the analysis. The PQ version considered in this paper is a nineteen-item questionnaire with a seven-response Likert scale. The Likert formatting ranged from \"Not at all\" to \"Completely\". \begin{table}
\begin{tabular}{l c c c} \hline
**SSQ Items** & **Nausea** & **Oculomotor** & **Disorientation** \\ \hline
1. General discomfort & O & O & \\
2. Fatigue & & O & \\
3. Headache & & O & \\
4. Eyestrain & & O & \\
5. Difficulty focusing & & O & O \\
6. Increased salivation & O & & \\
7. Sweating & O & & \\
8. Nausea & O & & O \\
9. Difficulty concentrating & O & O & \\
10. Fullness of head & & O & O \\
11. Blurred vision & & O & O \\
12. Dizzy (eyes open) & & & O \\
13. Dizzy (eyes closed) & & & O \\
14. Vertigo & & & O \\
15. Stomach awareness & O & & \\
16. Burping & O & & \\ \hline _Total_ & (1) & (2) & (3) \\ \hline
**SSQ Components** & & **Computation** \\ \hline
1. General discomfort & & (1) \(\times\) 9.54 & \\
2. Fatigue & & (2) \(\times\) 7.58 & \\
3. Headache & & (3) \(\times\) 9.56 & \\ \hline _Total score (TS)_ & & ((1) + (2) + (3)) \(\times\) 3.74 & \\ \hline \end{tabular}
\end{table} 
Table 2: Simulation Sickness Questionnaire (SSQ). Each subject must complete the following procedure:  
1. **Signing of the participation agreement (personal data disclaimer)**
2. **Completion of SSQ questionnaire (SSQ1)**
3. **Stage 1 (ST1, 10 min). ** Familiarization with the VR technology using the Steam VR room. The user is asked to explore the room and recognize the boundaries of the play area, shown virtually through a blue mesh. ST1 lasts 10 min. 4. **Completion of SSQ questionnaire (SSQ2)**
5. **Stage 2 (ST2, 30 min):** 5.1.