# Analysis of the Motion Sickness and the Lack of Comfort in Car Passengers
## 4 Relative Statistical Analysis
### General Confort Analysis  
The first part of the analysis focuses on frequencies higher than 1 Hz, that is, accelerations which are believed to cause what is known as general discomfort. As it has been previously explained in Section 1, both \(A_{v}\) calculated by Equation (2) and \(N_{i}\) could be used for this purpose. \(N_{i}\) represents the times that acceleration data exceed a certain threshold considered to cause discomfort, which has been set to 2 m/s\({}^{2}\). Figure 6 shows a comparison between drivers, cars and sections when \(A_{v}\), \(N_{x}\), \(N_{y}\) and \(N_{z}\) are considered. The percentages of situations where car \(i\) exceeds car \(j\) (Figure 6a) or driver \(i\) exceeds driver \(j\) (Figure 6b) or section \(i\) exceeds section \(j\) (Figure 6c) for the comfort variables are shown. Each specific color represents each car or driver or section, and they are compared one by one. When the difference between the calculated variable is less than 5%, situations which have been considered as non-determinant, it is represented in beige. That is, in Figure 6b, D1 (red) is compared against D2 (blue) and D3 (green), and next, D2 (blue) is compared against D3 (green). If \(A_{v}\) is analyzed, on the one hand, it can be concluded that in 60% of the situations D1 presents a higher \(A_{v}\) than D2, in 10% a lower \(A_{v}\) and, in the remaining cases (beige), it could be considered very similar values. On the other hand, D1 always presents higher values of \(A_{v}\) than D3.  
Considering this figure, taking vehicle differences into account, when comparing C1 and C2 (Figure 6a), it can be concluded that C2 exceeds the threshold in the longitudinal axis (\(N_{x}\)) more frequently than C1 does, but in the lateral axis (\(N_{y}\)), just the opposite happens. Attending to \(N_{z}\), we cannot conclude anything, since in half of the situations, C1 outperforms C2 and the other half vice versa. Concerning \(A_{v}\), even though the greatest values are related to car C1, the differences between C1 and C2 are too small and almost all the recorded \(A_{v}\) values belong to the same discomfort level. Furthermore, if the threshold to distinguish the two values increases, the percentage of times that C1 exceeds C2 decreases significantly (see Figure 7).  
Figure 6: Comparison between drivers, cars and sections when \(A_{v}\), \(N_{x}\), \(N_{y}\), \(N_{z}\) are considered. The percentages of situations where car \(i\) exceeds car \(j\) (**a**); driver \(i\) exceeds driver \(j\) (**b**); and section \(i\) exceeds section \(j\) (**c**) for each particular variable.  
On the other hand, concerning driver comparison (Figure 6a), differences can be seen in their driving style. As all variables show, it can be undoubtedly concluded that D3 is the one who drives most comfortably and D1 the least.  
Finally, the results for the different sections are analyzed. As a consequence of the difference in their length, in order to compare them, \(N_{x}\), \(N_{y}\) and \(N_{z}\) have been averaged in distance. Undoubtedly, S3 is the one in which the threshold is surpassed the least in all directions and \(A_{v}\) is smallest, S1 is the second most comfortable, whereas S2 and S4 are the worst ones. S4 is less comfortable if longitudinal (\(N_{x}\)) and vertical (\(N_{z}\)) axes are considered, whereas S2 is less comfortable in lateral direction (\(N_{y}\)). The value of \(A_{v}\) is similar for S1 and S2 sections, and the S4 section is more comfortable in this sense than the other sections.