Effect of scale on the links between walking and urban design

Studies of the relationship between walking and urban form consistently show that pedestrian-friendly neighbourhoods encourage local walking. However, the geographic scale of measurement of the built environment for developing walkability indices and their relationship with different types of walking (e.g. for transport and recreation) has not been fully examined. In this study, objective measures of the built environment were developed at three geographic scales: suburb, census collection district, and 15min walk neighbourhood for each participant. Walking for transport and recreation within the neighbourhood was measured using the Neighbourhood Physical Activity Questionnaire. The likelihood of walking at all (yes/no) and as recommended for health benefit (150min per week) were assessed using logistic regression. The walkability index captured a strong positive relationship between urban form and walking for transport, but found no relationship at any scale for recreational walking. Participants walking for transport and living in high versus low walkable areas were 63% more likely to walk at the suburb scale (odds ratio 1.63; 95% confidence interval 1.22-2.18), twice as likely to walk at the census collection district scale, and nearly three times more likely to walk at the 15min walk scale (odds ration 2.79; 95% confidence interval 2.09-3.73). The scale at which environmental data are measured influenced the strength of the relationship, showing that the neighbourhood 15min from home was most predictive of transport walking. This has research and policy implications. Standardised scales across studies would both improve comparability of results and enhance understanding of the influences on walking.