In this study, to conduct research on thermal comfort during actual driving in summer and winter, biological signals such as skin temperature, heart rate variability, and electroencephalogram of the driver were measured and subjective questionnaires such as thermal sensation vote, thermal comfort vote, and concentration level vote were investigated. Furthermore, HVAC cooling mode, HVAC with ventilation seat cooling mode, and HVAC with water seat cooling mode were used as indoor cooling methods in summer, and HVAC heating mode, seat heating mode, and HVAC with seat heating mode were used. Besides, biological changes of the driver with time were studied experimentally.
When HVAC cooling mode was used during actual driving in summer, it was effective in improving the indoor thermal environment, activating the driver’s parasympathetic nerve, and improving the Valence of brain waves, but the driver’s response to the HVAC cooling effect decreased. And although the thermal comfort was increased, it did not maintain for a long time. When HVAC cooling mode and ventilation seat were used simultaneously, it contributed to maintaining skin temperature, activating parasympathetic nerves, increasing concentration level, properly maintaining Valence and Arousal, and improving the driver’s thermal comfort. Within a short period of time, using HVAC cooling mode and water seat were used, it contributed to decreasing skin temperature, activating parasympathetic nerves, and improving concentration level, Valence, and Arousal, but these indicators and thermal comfort were reduced when it used for a long time.
In winter, when HVAC heating mode was used during actual driving, it was effective in improving the thermal environment in a short period of time, increasing the driver’s skin temperature, activating parasympathetic nerves, and improving Valence and Arousal, but when used for a long time, the driver became thermally discomfort. When the seat heating mode was used, the thermal environment could not be greatly improved, but the driver’s skin temperature was increased, parasympathetic nerves were activated, and concentration level and Valence increased, and these conditions were continued. However, the Arousal of the driver could not increase. When HVAC with seat heating mode was used, the thermal environment was greatly improved, and the driver’s skin temperature increased, parasympathetic nerves were activated, and concentration level, Valence, and Arousal were improved, but thermal comfort was reduced due to excessive heating when this mode was used for a long time.
Driver’s physiological and psychological reactions were relative and time differences among them could occur. When cooling and heating modes were used during actual driving in summer and winter, the driver’s physiological changes tended to appear later than changes in the thermal environment, and the driver’s psychological changes tended to appear later than the driver’s physiological changes. If appropriate cooling and heating methods are used during driving in summer and winter, it can provide good thermal comfort to the driver in a short time and also reduce the power required by the HVAC system, and then it is effective in terms of energy.