Principles of dense, mixed-use environments and pedestrianisation are influential in urban planning practice worldwide. A key outcome espoused by these principles is generating “urban vitality”, the continuous use of street sidewalk infrastructure throughout the day, to promote safety, economic viability and attractiveness of city neighbourhoods. Vitality is hypothesised to arise from a nearby mixture of primary uses, short blocks, density of buildings and population and a diversity in the age and condition of surrounding buildings. To investigate this claim, we use a novel dataset of 2.1 million time-lapsed day and night images at 145 representative locations throughout the city of Accra, Ghana. We developed a measure of urban vitality for each location based on the coefficient of variation in pedestrian volume over time in our images, obtained from counts of people identified using object detection. We also construct measures of “generators of diversity”: mixed-use intensity, building, block and population density, as well as diversity in the age of buildings, using data that are available across multiple cities and perform bivariate and multivariate regressions of our urban vitality measure against variables representing generators of diversity to test the latter’s association with vitality. We find that two or more unique kinds of amenities accessible within a five-minute walk from a given location, as well as the density of buildings (of varying ages and conditions) and short blocks, are associated with more even footfall throughout the day. Our analysis also indicates some potential negative trade-offs from dense and mixed-use neighbourhoods, such as being associated with more continuous road traffic throughout the day. Our methodological approach is scalable and adaptable to different modes of image data capture and can be widely adopted in other cities worldwide.

中文翻译：

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使用延时街景图像和对象检测测量城市活力，以对人行道动态进行可扩展评估


密集、混合用途环境和步行化原则对全球城市规划实践具有影响力。这些原则所支持的一个关键成果是产生“城市活力”，即全天持续使用街道人行道基础设施，以促进城市社区的安全、经济可行性和吸引力。据推测，活力源于附近主要用途、短街区、建筑物和人口密度以及周围建筑物年龄和状况的多样性。为了调查这一说法，我们使用了一个新的数据集，其中包含加纳阿克拉市 145 个代表性地点的 210 万张延时昼夜图像。我们根据图像中行人体积随时间变化的变异系数，从使用对象检测识别的人数计数中获得，为每个位置开发了一种城市活力的衡量标准。我们还构建了“多样性生成器”的度量：混合用途强度、建筑、街区和人口密度，以及建筑物年龄的多样性，使用多个城市可用的数据，并根据代表多样性生成器的变量对我们的城市活力度量进行二元和多元回归，以测试后者与活力的关联。我们发现，从给定位置步行 5 分钟即可到达两种或多种独特的便利设施，以及建筑物的密度（不同的年龄和条件）和短街区，与全天更均匀的客流量相关。我们的分析还表明，密集和混合用途社区会带来一些潜在的负面权衡，例如与全天更连续的道路交通相关联。 我们的方法论方法具有可扩展性，适用于不同的图像数据采集模式，并且可以在全球其他城市广泛采用。