###### Abstract
Thus, the recorded increase in the safety of vehicles and infrastructures must necessarily be associated with interventions and measures able to determine positive impacts on the driver's behavior. To effectively direct the interventions in this context, it is useful to increase the knowledge and understanding of the driver during the driving activity, investigating also their emotional states. Studies and researches about this subject were conducted in various fields and disciplines. The complexity related to these studies lies in the component of subjectivity associated with emotional states. For example, considering stress, it can be observed that, typically, the reaction of the human body to a stressful situation can be identified with an increase in heartbeat, muscle tension, blood pressure, and sweating [4; 5; 6]. However, the factors and elements that can determine the onset of a state of stress, and its related \"degree\" of stress, can vary widely depending on each individual subject and, for the same subject, depending on many internal variables (such as stress collected during the day, emotional factors, or moods). Trying to assess the psychophysical state of a person as objectively as possible, methods evolved from simple questionnaires to a direct evaluation of parameters, allowed by new and smarter technological possibilities. In the analyses performed within this study, the physiological signals taken into consideration, according to the literature review, were heartbeat (in particular, heart rate variability (HRV) and some of its components), skin conductivity (galvanic skin response (GSR)), and respiratory rate (RR) [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21]. These parameters and their functionality are described together with the method. The research described in this paper is oriented to the study of the psychophysical state of the user driving a car, investigating conditions of particular stress, and contrarily, of considerable relaxation as possible causes of distraction, to increase the knowledge of these conditions during driving activities, and to provide elements of possible support for preventive accidental analysis. The main objectives can be summarized with the following three points:  
* Definition of a method for the identification of stressful/relaxing points for the driver;
* Validation of the method through the development and testing of an experimental protocol;
* Identification of possible correlations between stressful/relaxing points and black spots, identified through accidental analysis. It should be underlined that investigation of the driver's psychophysical state was performed in several previous studies [22; 23; 24; 25; 26; 27; 28; 29; 30; 31]. The added value of this paper is an investigation into how this aspect influences driving activity, in particular, the probability that high levels of stress or relaxation could impact on-road safety issues, supporting a preventive approach for road safety analysis. Among all the remarkable elements, it must be taken into account that dynamic tests with wearable and comfortable tools were carried out in the real world, while, in other methodologies, the tests were mainly performed in protected environments or with driving simulators.