## 2 Experimental Setup and Methods
### Driving Simulator and Bio-Signal Measurement Device  
An experiment was conducted using a driving simulator to provide the subject with an environment similar to a real driving condition. The driving simulator used a G27 racing wheel (Logitech, Inc.) and driving simulation software (City Car Driving 1.5, Forward Development, Inc.) was used. To measure the variations in the physiological signals according to changes in the indoor temperature and vent discharge air temperature of the vehicle during driving, the physiological signals of the drivers were measured and analyzed by installing EEG and PPG measuring equipment and a thermal-imaging camera. The pulse wave (PPG) was measured using uBioMacpa (BioSense Creative, Inc.), which is an optical volume pulse wave device using infrared rays. During the experiment, subjects abstained from excessive movement for the precise measuring of bio-signals. Figure 2 shows a picture of a worn pulse wave measuring device, and Table 4 shows the specifications of the pulse wave measuring device. The pulse wave is a waveform representing the vascular volume fluctuations transmitted to the peripheral arteries, and it is possible to investigate the conditions of autonomic nerve balance, stress index, and heart rate distribution by using the analysis of the pulse wave. The stress index can be displayed by analyzing the range of autonomic nerve rhythm, and the autonomic nerve balance (LF (low frequency)/HF (high frequency)) is the ratio of sympathetic activity to parasympathetic activity. It is also an index of immunity of the body. Total power (TP) indicates the epidemic fever of the patient. When it is lower than the normal value, it means that the autonomic nerve control ability and the immunity decreased, and the ability to regulate against the external environment and the ability to respond to stress decreased. In addition, the standard deviation of N-N interval (SDNN) indicates the standard deviation of the pulse from the external environment. When it increases, the condition of subject is stable. Using the root mean square of successive differences (RMSSD) is a method to check the parasympathetic activity by evaluating the mean deviation of the heartbeat. Figure 3 shows the locations of the EEG measurement sensors mounted on the subject, and Table 5 represents the specifications of the EEG measurement equipment. The EEG measurement was performed using QEEG-16 (LAXTHA, Inc.), and it has an EEG cap with 16 measurement sensors according to the International 10/20 system. Fp1 and Fp2 are the prefrontal lobes, and F3, F4, F7, and F8 indicate the position of the prefrontal lobes. C3, C4, \begin{table}
\begin{tabular}{c c} \hline
**Item** & **Specification** \\ \hline Measuring range & 40–200 BPM \\ Measurement error & \(\pm\)2\% \\ Band pass filter & 0.15–4 Hz \\ \hline \end{tabular}
\end{table} 
Table 4: Specifications of the PPG measurement device. Figure 2: Image of the PPG measurement. P3, P4, P7, and P8 are the positions of the parietal lobes, T7 and T8 are the temporal lobes, and O1 and O2 are the occipital lobes. Human brain waves are roughly classified into \(\delta\)-, \(\theta\)-, \(\alpha\)-, \(\beta\)-, and \(\gamma\)-waves. The \(\delta\)-wave is 0.5 to 4 Hz, and it appears in deep sleep and inner consciousness. The \(\theta\)-wave is 4 to 8 Hz, and it is generated in sleepiness and shallow sleep. The \(\alpha\)-wave is 8-15 Hz, and it occurs in a comfortable state or when the eyes are closed. In addition, the sensory motor rhythm (SMR) wave of the \(\alpha\)-wave is 12-15 Hz, and it is generated in a slight state of tension, such as during attention and concentration. The \(\beta\)-wave is 14-30 Hz, and it occurs in a state of concentration or anxiety and tension. The \(\gamma\)-wave is more than 30 Hz, and it is present in anxiety and excitement. In this study, the \(\beta\)/\(\alpha\)-wave ratio was analyzed. A higher value means improved concentration because the \(\beta\)-wave increases. A lower value indicates a comfortable state because the \(\alpha\)-wave increases.