## 3 Consideration  
First, it was verified whether participants were really surprised at the appearance of the unexpected vehicle and whether their blood pressure increased. It is known that respiration shows a person's tension, thus the timing of perspiration from the unexpected vehicle shows whether participants were really surprised at the appearance of another vehicle. Figure 8 shows the average time \(\pm 1\) SD of all participants to increase the perspiration value from the point of the appearance of the vehicle based on the algorithm introduced above; however only \(\lambda\), the penalty value, was changed to 15 because the change points seemed to be earlier than the timing of blood pressure increase. In Figure 8, left means time to increase the perspiration value of the left thumb, right means the time to increase the perspiration value of the right thumb, and min (L, R) means the minimum time of \"left\" and \"right\". Eleven out of thirteen participants had a perspiration response, and from Figure 8, the time from the appearance of the unexpected vehicle to triggering a perspiration response in the left or right thumb seems to be approximately nine sec. The timing of the increase in mean blood pressure from the time the unexpected vehicle appeared was calculated based on the algorithm presented above. To detect this timing, the changepoint method was applied. From the results of the calculations by the changepoint method, the average increasing time of \(\pm 1\) SD of all participants is shown in Figure 9. Here, in Figure 9, \"\(\mu\)BP-mp\" means the timing based on the blood pressure measured by the contact type blood pressure monitoring system (\(\mu\)BP-mp) and \"IR\" means the timing based on the blood pressure measured with infrared radiation type noncontact blood pressure monitoring system. Because this infrared noncontact blood pressure monitoring system is noncontact, the timing of the developed blood pressure increase may be significantly longer than that of a contact-type. The detection time by the developed system was found to be approximately 2.5 s shorter than that of the contact type continuous blood pressure measurement system; however, there is no significant difference about the detection time between these blood pressure monitoring systems. For in-vehicle applications, a delay in the detection timing of blood pressure changes could lead to a serious accident because a system cannot detect driver's state and warn him/her immediately. Therefore, changes in blood pressure must be detected immediately to ensure driver safety; in other words, the timing of blood pressure change detection must not be delayed compared to the conventional contact type blood pressure monitoring system, and it is necessary to show statistically that there is nodifference in the detection timing between the two, i.e., \(\mu\)BP-mp and IR. The result of this experiment states that the developed noncontact blood pressure monitoring system is as good as the conventional system, statistically. This means that there is statistically no difference in detection delay between the noncontact and contact blood pressure monitoring systems. Therefore, the developed system can be useful for detecting a driver's psychological state change immediately, such as surprised state as shown in this experiment. As far as we know, there exists no previous published work discussing the relationship between the times when perspiration occurs and when blood pressure increases, as they pertain to a driver's state of surprise. However, consideration of the results suggest that the timing of increased blood pressure follows that at which perspiration occurs; this knowledge may be used to help conceive the mechanism of bio-mechanism or nervous system. Considering the results reported in this study, we would like to propose a human-machine interface (HMI) for advanced driver-assistance systems (ADAS).