# Analysis of the Motion Sickness and the Lack of Comfort in Car Passengers
## 8 Discussion  
Based on the results obtained in Sections 4-7, an exhaustive analysis of them has been performed by studying the repercussion of the type of road, the car and the driving style on the lack of comfort of the passenger. Once the results and the feedback of the passengers have been analyzed, this section collects the main conclusions of the experimental campaign. It is worth noting that in every direction, the frequency of the accelerations ranges from 0 Hz to 0.3 Hz (see Figures 10 and 11) for every car, driver and section and that in the vertical direction, there is a low-power characteristic frequency located at 2 Hz. Therefore, attending to general discomfort (filters focused on higher frequencies), none of the situations are specially uncomfortable. This correlates with calculated Av values, which according to Equation (2) are _'not or little comfortable'_. Passenger feedback confirms the mentioned result. Additionally, all variables have been separately compared by axes for every car, driver and section. It has been verified that not only \(N\) but also \(MSDV\) have a significant smaller value for their vertical axis than for the other axes. This implies that the attention has to be paid to the lateral and longitudinal axes, which strongly agrees with the last work done by [PERSON] and [PERSON] [6; 35; 39; 40; 41] and conflicts with the ISO norm [37]. The study reveals that the type of road and its characteristics significantly influence the results of the comfort variables. On the one hand, both \(N\) and \(MSDV\) prove that, undoubtedly, section S3 is the most comfortable in every sense. S1 is considered the second most comfortable taking all variables except \(MSDV_{z}\) into account. Paying attention to the spectrogram of the vertical axis of S1 in Figures 10 and 11, it is clear that much power is located at low frequencies and in the first part of the travel. After completing the journey again, it has been observed that, in the beginning of section S1, the pavement is irregular and rough which implies that, only taking \(MSDV_{z}\) variable into account, S1 is more uncomfortable than S2. On the other hand, S4 is the least comfortable section if longitudinal and vertical axes are considered (bigger \(N_{x}\), \(MSDV_{x}\) and \(N_{z}\)) and lateral low frequencies are evaluated (bigger \(MSDV_{y}\)), whereas S2 is less comfortable in the lateral direction when high frequencies are considered (bigger \(N_{y}\)). This matches with the section characteristics because, as it has been explained in Section 3, S3 is a headway, S2 has a lot of curves, whereas S4 has roundabouts, pedestrian crossings, traffic lights and bumps. In addition, kernel analysis demonstrated that all the three drivers with both vehicles exhibit a more spread kernel in S2 and S4 (see Figure 9b), which means that the characteristics of the section themselves lead to more irregular drivings. Furthermore, the spectrograms (Figure 10) depict a similar pattern in every section for every driver, which confirms that the features of the section are responsible for certain accelerations. Passenger feedback coincides with the previous results as it characterizes the lack of comfort of the sections in the same way as the variables do. Moreover, with regards to section S1 and \(MSDV_{z}\), no passenger did identify that section to be uncomfortable which shows that, indeed, the lateral and longitudinal axes contribute in a more substantial way than the vertical axis does. Concerning driver comparison, it can be seen that driving style emphasizes the level of discomfort and fatigue that passengers suffer across the whole journey. Thus, as all variables show, it can be undoubtedly concluded that D3 is the one who drives most comfortably. On the other side, D1 is the least comfortable one, while D2 can be characterized as an intermediate one.