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Urban planners and transportation professionals studied how urban form is related to walking and cycling for transport, transit use, traffic congestion, air quality and open space conservation. 1 - 5 Active transportation is consistently positively associated with urban form variables of greater mixed land use, street connectivity, residential density and combinations of these variables. 6 - 8 Urban form is related to the total amount of physical activity for recreational and transportation purposes. 9 - 13 People living in more "walkable" and "bikeable" neighbourhoods with homes in proximity to non-residential destinations are less likely to be overweight or obese than people living in more suburban neighbourhoods that require motorised transportation. 11 13 - 15 Improving the built environment to make it easier for people to be physically active, in part through more active transportation, is an essential component of increasing physical activity. 16 - 19
However, some investigators have either not found such an association or have found weak relations between built environment factors and active transportation. 20 These investigators posit that it is not clear which urban form factors are the most influential on active versus non-active transport. This necessitates further research and better specification of the urban form variables most influential on active transport.
Ways of measuring urban form in physical activity studies
This paper focuses on the systematic measurement of urban form to enhance the study of active transportation and physical activity. To date, measurement of walkability variables has included expert opinion about community typology, 5 census data, systematic observations, 12 21 land-use databases using Geographic Information Systems (GIS), 22 and a regional "sprawl index". 1 The urban form variables evaluated have been numerous, including land use mix, street connectivity, sidewalk availability, building setbacks and dozens of others.
Given the large number of potential built environment factors that may influence transportation mode choice, there has been interest in deriving composite factors that combine multiple aspects of community design. Cervero and Kockelman developed such measures through factor analysis in an attempt to operationalise the larger constructs of density, diversity and design (the 3 Ds) from a variety of built environment variables within 50 San Francisco Bay area neighbourhoods (single or clustered census tracts). 23 Using a different geographic unit of 150m grid cells,...