Built form affects perceived safety

Chester Harvey et. al, "Effects of skeletal streetscape design on perceived safety,"Urban Landscape and Urban Planning 142 (2015): 1

Abstract: It is important for planners and urban designers to understand how physical characteristics of urban streetscapes contribute to perceptions of them as safe, comfortable urban spaces. While urban design theory offers numerous suggestions for successful streetscapes there is meager empirical evidence of their effects. We suggest that this is largely due to precision and sample size limitations on audit-based physical design and human perception measurements. This paper overcomes these limitations by identifying a key set of “streetscape skeleton” design variables that can be efficiently measured using a GIS-based method. It then measures these variables on a large and diverse sample of streetscapes, and examines their relationship to crowdsourced perceived safety scores, a useful indicator of environmental comfort. Regression modeling indicates that factors related to streetscape enclosure have a substantial positive effect on perceived safety. These include street tree canopy, the number of buildings along a block, and the cross-sectional proportion—the ratio of building height to width across the street between building façades. Importantly, these streetscape-scale skeleton variables have greater effect than neighborhood-scale urban form and affluence measures that are commonly used to identify desirable urban environments. Planning practitioners can draw on our results to set priorities for urban forestry and design guidelines that shape the spatial proportions of streetscapes and their success as spaces that feel safe and comfortable for human users.

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Highlights (quoted from ScienceDirect):

• Building and tree design characteristics affected perceived safety of streetscapes.
• Trees positively affected safety perceptions more than building-related variables.
• Tall, narrow streetscapes were perceived as safer than short, wide streetscapes.
• More buildings per length of streetscape increased perceived safety.
• Urban form and affluence affected perceived safety less than streetscape design.