Uncovering the relationship among spatial vitality, perception, and environment of urban underground space in the metro zone

With the rapid development of rail transit, effectively developing urban underground space (UUS) in the metro zone has become an important approach to expanding urban space. However, UUS is currently facing problems, such as an uneven distribution or even loss of vitality, which restricts the utilization efficiency of the space. Thus, we established a UUS environmental assessment system based on the “comfort-aesthetic-function-traffic-structure” using space syntax, instrumental measurement, and questionnaire surveys. By constructing a partial-least-square structural equation model, the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas, namely the underground transportation-oriented space (transportation space for short) and the underground commercial-oriented space (commercial space for short), were studied in detail throughout the working day. Results indicate the following: (1) the UUS in the metro zone environment influences spatial vitality. The vitality distribution of transportation space is significantly affected by the spatial traffic and structure. The vitality distribution of commercial space is significantly affected by the spatial function and traffic. (2) The environment of UUSs in the metro zone influences users's perception. The perception of transportation space is significantly affected by aesthetics and comfort. The perception of commercial space is significantly affected by aesthetic, comfort, and spatial functions. (3) The user's perception affects vitality, and the effect is more significant in commercial space. This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones. Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.