When do we shop, and how do we get there?

The following description of consumer travel uses cross-sectional travel survey data from the 1996 and 2001 Transportation Tomorrow Survey (TTS). These data have been combined with information from the CSCA retail databases on the geographical distribution of power retail and enclosed mall destinations in 1996 and 2001. The method involved matching TTS trip-ends (identified by traffic zone) with the location of retail opportunities extracted from the CSCA databases. Exploratory analysis confirms that the dominant retail feature within traffic zones visited for shopping purposes is either a retail power centre or enclosed mall (Mitchell, 2006). Estimates of vehicle kilometres travelled (VKT) have been developed by multiplying the number of auto-driver trips (single-occupancy vehicle, or SOV, trips) between a trip origin location and a zone containing retail, along the shortest path connecting the two zones.13 The cost (impedance) factor for the shortest-path analysis assumes free-flow conditions under the posted speed limit.14

13. 1 vehicle kilometre travelled = 1 vehicle x 1 km of travel. In the TTS, an auto-driver trip is equivalent to a single occupancy vehicle trip (SOV), or the movement of a single vehicle. In other words, 1 auto-driver trip is equivalent to the movement of 1 vehicle.
14. For a discussion of the role of congestion in this context, see Buliung et al. (2007).