Design is in the details: a scoping review of human-scale physical design interventions’ impacts on active travel behaviour

Most studies on the built environment and travel nexus measure the built environment at the city-region or neighbourhood levels and overlook human-scale design, which tends to have outsized effects on active travel. To address this gap, we conducted a scoping review of empirical studies that examine how human-scale physical design interventions such as sidewalks, bike lanes, street landscape, and signage influence walking and biking. We synthesised study findings with respect to intervention types and their documented impacts, and common methodological approaches and limitations. We find that various human-scale design features are associated with increased walking and biking activities, often accompanied by mode shifts. These design interventions improve built environmental quality in terms of safety, equitable accessibility, and neighbourhood amenity, which may encourage more walking and biking, which, in turn, can generate environmental and economic benefits. We also find that cross-sectional studies test the association between specific design features and walking and/or biking, but have offered mixed and scattered evidence, largely because different studies have measured design features and travel outcomes differently. Before-and-after studies often evaluate design interventions in bundles and tend to offer better causal evidence, especially those using treatment-and-control designs and longitudinal data. Recent developments in data technology and methodology offer opportunities to improve measurement and causal inference. Existing evidence suggests that, in practice, human-scale design to encourage active travel needs to consider specific local contexts and targeted users, bundle different physical interventions, and complement physical design with educational programs, stakeholder engagement, and post-implementation monitoring to maximise benefits and minimise unintended effects of the design interventions.