Assessing the Visual Complexity of Urban Form: A Typology of Measures and Indicators

Visual complexity, alongside other forms of complexity in cities, serves as a daily stimulus in the perception of urban environments. Various studies have addressed optimal visual complexity and the organization of environmental data, considering the limited processing capacity of the human brain. Despite significant prior research, the challenges of quantifying visual complexity, the scarcity of indicators that predict perceptual complexity, and the dispersion of existing indicators across multiple disciplines have resulted in a lack of clarity and validity in this field. This study aims to establish a precise definition of complexity, particularly visual complexity, in relation to the physical structure of cities, and to present a comprehensive classification of visual complexity indicators applicable to urban design scales. To achieve this, the study reviews related literature from the fields of aesthetics, environmental psychology, architecture, and urban design to identify the factors influencing the visual complexity of urban forms. Additionally, a typology of methods for measuring visual complexity is presented in a table, categorized into two main groups: the first group includes methods that use urban landscape elements as units of complexity measurement, while the second group comprises methods that consider the informational units received from the visual environment as the measurement units. Given the importance of assessment scale in measuring complexity, a six-level hierarchy for evaluating indicators is proposed. This table serves as a comprehensive summary, potentially functioning as an effective tool for analyzing and determining the optimal level of visual complexity in relation to urban form. It can help prevent confusion in studies related to environmental complexity. Furthermore, the study highlights the importance of movement in the perception of complexity, the role of attention, the impact of semantic dimensions, and familiarity with the environment as factors that distinguish urban complexity studies from those in other fields.