Urban form and physical activity through transport: a review based on the d-variable framework

The potential to encourage physical activity through the use of active transport modes, particularly walking and cycling, is of interest to public health and planning professionals alike. The way elements of urban form, such as density, destination accessibility, design, distance and diversity can either promote or discourage active transport use, is a well-developed area of research. While this research body has been examined previously, urban form is often conceptualised in varying ways, resulting in review recommendations that are difficult to operationalise in subsequent urban and transport planning research. This review takes a fresh perspective on the research by undertaking a narrative review of 104 quality assessed articles examining the impact of elements of urban form on walking and cycling. Urban form is conceptualised using the well-known D-variable framework. We found that the impact of urban form on active transport was expressed in 293 measurements, and that 95.5% of these measurements were positively correlated with the use of walking and/or cycling for transport. We conclude that differences in the built environment are related to differences in the use of physically active modes–active travel is practised in environments where distances are shorter, the distribution of uses are mixed, and infrastructure, including transit, is tailored and accessible. Furthermore, while the D variables framework remains effective for conceptualising this link, this review reveals ways that the framework to be used in a more comprehensive, specific and practical way.