Effects of solar radiation in the streets on pedestrian route choice in a city during the summer season

There is a hypothesis that on severe hot weather days, pedestrians may choose routes based on the presence of solar radiation. However, this hypothesis is yet to be verified. Therefore, the present study experimentally clarified the effect of solar radiation in streets on pedestrian route choice. In the experiments, nineteen participants walked freely from the starting point to the designated destination on a sunny summer day. The area for the experiment is a commercial area around the Tokyo Station, which is the central area of Tokyo, Japan. In the experiment, participants were asked to verbalize the reasons for their route choices at every diverging point during their walk. The results are as follows: Most participants chose shaded routes in front of a large commercial facility. The most common reason given was "because there is shade" (28.2%), indicating that the presence or absence of shade is a major factor in route choice under severe thermal environment. Furthermore, in the questionnaire conducted after the walk, the most common reason participants provided for choosing shade was to protect their health, such as preventing heat stroke and sunburn. In summary, participant responses indicated their awareness of the dangers of solar radiation and their defensive motivation to avoid it, which might have led them to prioritize shade over other reasons in their route choice. The clarification of the effect of solar radiation on pedestrian route choice and the reasons for choosing shaded areas is very useful for future consideration in building design and urban planning.