*3.7. Procedure Description*

First, the sensors were fitted to the participant, who then completed the initial survey. Then, he or she listened to Mozart's Sonata for Two Pianos in D major using headphones. This track has been selected because it improves mental function [93]. The objective of this phase is to be relaxed before the driving test and to stabilize the sensors. A total of 50 drivers with an average age of 31.76 years (max: 57, min: 18; std. dev.: 10.48) and driving experience of 11.28 years (max 40, min: 1, std. dev: 10.24) participated in the experiment. The participants drove for 25 min. In the driving test, the heart signal, the skin conductivity and the environment (temperature, humidity and CO2 level) were monitored. The music and the sounds of the vehicle were listened to through headphones. The drivers had to complete the routes proposed by the GPS of the driving simulator. Each route has a length of 5 km and its level of di fficulty is comparable because the concentration of vehicles and pedestrians is the same in all cases. The driving simulator assigns points to the participant at the beginning of the route. Each time an infraction is committed, points are deducted. When the score is zero, the route must be repeated. This allows the participant to be focused on the driving task as if in a real environment [94]. The driving time is 25 min to have enough time for the stress data to be valid [95].

A statistical analysis was conducted using R (version 3.6.0) in order to obtain conclusions from the data. We have used the Student's test or Wilcoxon's test for independent samples depending on whether the hypothesis of normality is verified or not. The significance level was set at 0.05. Therefore, if the *p* value is less than 0.05, we assume that there are significant di fferences between the analyzed groups.
