# Analysis of Development Coordination Levels between Skywalk Systems and Urban Spatial Environments
## 1 Introduction  
The acceleration of urbanization, population explosion, and land use constraints has led to a number of challenges for high-density cities, including insufficient basal capacity and spatial fragmentation [1]. The traditional planarized development mode is no longer aligned with contemporary society's demand for composite space [2]. As a result, three-dimensional transportation has become an effective means of addressing these issues [3]. Skywalk systems are vital components of three-dimensional transportation infrastructure, which refers to the above-ground level that connects buildings and spaces through corridors to provide safe, comfortable, and convenient pedestrian access [4]. The development of skywalk systems can be traced back to the middle of the 20 th century, initially emerging in North American cities, such as Minneapolis, Montreal, and Toronto. Its primary purpose was to mitigate the challenges posed by cold climates, protecting the pedestrians during their walking trip. By the end of the 20 th century, skywalk systems had also been developed in some cities in Asia, such as Hong Kong, China, Singapore, and Tokyo, with the focus having shifted to alleviating ground traffic congestion and enhancing the plot ratio. At present, skywalk systems serve three main functions. First, they connect public transportation stations with the surrounding commercial, office, residential, and other functional areas by creating a three-dimensional pedestrian system that combines the ground and underground, thus shortening the walking distance and time, and improving the convenience and comfort of public transportation [5]. Second, it increases the amountof above-ground public space, expanding the space for urban activities such as communication, and stopping and resting [6]. At the same time, it creates a large amount of gray space at the ground level through an elevated design to enrich the spatial interface. The third purpose is to create a distinctive urban landscape [7], such as New York's High Line Park, which was converted from an abandoned railroad, incorporating art installations and landscape design along the way, to become an iconic community activity space. Despite the importance of skywalk systems, their construction is met with some controversy. Skywalk systems are influenced by various aspects of the urban environment [8], and their advantages in promoting urban development are mainly reflected in two aspects: First, they are integrated into urban life as a critical component of three-dimensional transportation, thereby reducing the reliance on high-carbon-emitting transportation modes (e.g., private cars) in cities and mitigating tailpipe pollution from slow-moving vehicles [9]. Second, they can improve the efficiency of urban space utilization and promote the three-dimensional development of the city. By utilizing the space resources above the city, the potential of urban three-dimensional space can be exploited to relieve the pressure of ground transportation and conserve land resources [10]. However, these benefits do not apply to all cities [7; 11]; they are particularly effective in cities with relatively spacious streets, high white-collar employment rate, and cold and rainy weather, such as Minneapolis, St. Paul, Cincinnati, Toronto, Calgary, Edmonton, and Sapporo. Constructed skywalks also present challenges in four ways: Firstly, they can diminish the commercial vitality at street level, leading to a decline in ground-level retail activity, thus reducing the value of stores and discouraging ground-level engagement [12; 13]. Secondly, the privatization of public space becomes an issue, with the opening hours of the skywalk system being influenced by architecture and resources being taken away from public space [14; 15]. Thirdly, the lack of cohesive planning and management results in a fragmented system with subpar connectivity and accessibility [16]. Lastly, the construction cost is high, and the subsequent maintenance is challenging [8].