The density method uses the definitions of "Active Core" and
"Exurban" areas from the Transportation Method.
An Active Core is defined as a neighbourhood that has an average rate of active transportation, walking and cycling, 1.5 times higher than the overall average for the census metropolitan area. These census tracts are generally in central areas and the downtowns of cities. In some larger cities, Active Cores have begun to form in secondary centres outside of the downtown, such as Vancouver. In larger metropolitan areas, multiple Active Cores may also be older downtowns of towns that have now been absorbed into the larger CMA, such as St. Jerome in Montreal, Oakville in Toronto or Kitchener Waterloo and Cambridge. This is the reason for the designation of 'Active Core' as opposed to 'Inner City'. The results show that characteristics of the inner city may not simply occur in the geographic connotations of the term.
'Exurban' is defined as areas that have low density and mostly depend on automobile use. Though 'Exurban' is not included in the suburban category, many people may live in single detached homes and commute by auto to the Central City, as opposed to living a more agrarian lifestyle. We tried three different definitions of 'low density' for rural/exurban and settled on the Organization of Economic Co-operation and Development (OECD)'s rural communities definition, which is limited to areas that have less than 150 people per square kilometre. This is one of the methods used by Statistics Canada in their rural lands analysis (du Plessis et al, 2001).
The difference lies with the classification of the suburban areas. Instead of transport behaviour, census tract are classified by their potential for transit use based on population density. Four density models were tested, based upon criteria from classic transit planning literature (Pushkarev & Zupan, 1977), which are still used as a threshold for transit use today (Victoria Transit Policy Institute, 2010). From the various definitions, the two suburb classifications have been: 'Transit Supportive Suburb' and 'Auto Suburb'. 'Transit Supportive Suburbs' require a gross residential density greater than 17 units per hectare, which is considered an intermediate level of bus transit service. Auto Suburbs, while sharing the same name from the Transportation method are defined by a threshold of fewer than 17 units per hectare in this method.
However, even though this method only considered the gross density to support intermediate service (17 uph), few Canadian neighbourhoods have the density to justify this designation. This led to some strange comparisons with the Transportation Method because many neighbourhoods with some transit use did not appear to have the minimum density levels for economic bus service. This analysis may contribute to the discussion about why most Canadian transit services lose money. However, we decided to use the Transportation Method to classify suburbs because it is based upon people's actual behaviour in taking transit to work, rather than a more abstract measure of potential for transit use. Nonetheless, some of the Density Method maps are included for major cities so these comparisons can be made.