The article brings together the academic and industry literature on the design and management of urban airspace. We analyze the proposed airspace concepts, identify their strengths and weaknesses, point to gaps in research, and provide recommendations for a more holistic approach to designing urban airspace. We first identify the structural factors that define the size, capacity, and geometry of urban airspace. These factors are grouped into four categories: safety-related factors, social factors, system factors, and aircraft factors. Second, we review different urban airspace concepts proposed around the world. Third, we assess the airspace concepts based on the identified factors. Most of the reviewed airspace concepts are idealized as abstract networks, with an emphasis on maximizing safety and capacity, and with little regard for factors such as technological complexity, noise, or privacy. Additionally, we find that the airspace structure directly influences the level of safety, efficiency, and capacity of airspace. On the one hand, air vehicles in less structured airspace have more degrees of freedom. They can freely choose their position, altitude, heading, and speed, which increases airspace capacity and reduces flying costs. However, these concepts require high technological capabilities, such as dynamic geofences and advanced sense-and-avoid capabilities, to maintain the required safety levels. On the other hand, airspace concepts with fewer degrees of freedom can accommodate less capable aircraft but require strict operation rules and reduced capacity to ensure safety. Finally, the proposed urban air mobility concepts require extensive ground infrastructures, such as take-off and landing pads and communication, navigation, and surveillance infrastructure. There is a need for a new branch of research that analyzes urban air mobility from the perspective of urban planning, including issues around zoning, air rights, public transportation, real estate development, public acceptance, and access inequalities.

本文汇集了有关城市空域设计和管理的学术和行业文献。我们分析了拟议的空域概念，确定了它们的优缺点，指出了研究中的差距，并为更全面的城市空域设计方法提供了建议。我们首先确定了定义城市空域大小、容量和几何形状的结构因素。这些因素分为四类：安全相关因素、社会因素、系统因素和飞机因素。其次，我们回顾了世界各地提出的不同城市空域概念。第三，我们根据确定的因素评估空域概念。大多数经过审查的空域概念都被理想化为抽象网络，重点是最大限度地提高安全性和容量，并且很少考虑技术复杂性、噪音或隐私等因素。此外，我们发现空域结构直接影响空域的安全、效率和容量水平。一方面，结构性较差的空域中的飞行器具有更多的自由度。它们可以自由选择自己的位置、高度、航向和速度，从而增加了空域容量并降低了飞行成本。然而，这些概念需要高技术能力，例如动态地理围栏和先进的感知和规避能力，以保持所需的安全水平。另一方面，自由度较低的空域概念可以容纳能力较差的飞机，但需要严格的操作规则和减少的容量来确保安全。最后，拟议的城市空中交通概念需要广泛的地面基础设施，例如起飞和着陆平台以及通信、导航和监视基础设施。需要一个新的研究分支，从城市规划的角度分析城市空中交通，包括围绕分区、空中权利、公共交通、房地产开发、公众接受度和获取不平等的问题。